Preparatory work for C 3 line-list calculation

The goal of this dissertation is to study the infrared absorption spectrum of the C 3 (carbon three) molecule. In particular, the aim is to investigate its ground electronic state up to 12:500 cm-1, as this affects the atmospheres of cool C-rich stars. The linear C 3 molecule shows very unusual properties for a linear molecule: a high degree of floppiness, no permanent dipole moment and a strong bentstretch interaction. Consequently, the C 3 spectrum presents particular features such as overtones, hot bands, and, as has been recently detected in Carbon stars and molecular clouds, a quite low fundamental bending frequency (63 cm-1) when in the ground electronic state. This dissertation aims to address each of these features. The first section discusses the context for this work: the stars. It provides a brief introduction about the Astrophysics related to this research project. A review at the recent literature is provided and the experimental results which provide the goal for the results of the theoretical work in the rest of the dissertation are set out. The second section introduces the C 3 molecule and outlines its properties. Previous C 3 studies are discussed and the theoretical approach used to study ro-vibrational spectra of triatomic molecules is set out. Preparatory tests and calculations are carried out to allow a theoretical reproduction of C 3 roto vibrational spectrum in the infrared region to be produced. The third part of the thesis expands on the nuclear motion calculations of section 2 and presents the results of the large scale calculations performed using the DVR3D suit programs written by Tennyson et al. [1]. This program allows the calculation of energy levels, wave-functions, expectation values and Einstein Coefficients. It takes as input the Potential Energy Surface (PES) and a Dipole Moment Surface (DMS) constructed a priori (in section 2) by solving the electronic problem within the Born-Oppenheimer's approximation. Because the quality of the PES sets the accuracy of the ro-vibrational calculations tests on different C 3 PESs and DMSs are performed. To reproduce accurate spectra of cool stars atmosphere in the temperature range of 2000 - 4000 K it was necessary perform calculations with high rotational quantum number. For this reason, tests with J>>0 were necessary to optimize the DVR3DRJZ parameters in order to guarantee a certain degree of accuracy and energy levels convergence. The results of these calculations and associated C 3 line-lists should be very useful to support the observations and model atmospheric studies. This work was generously supported by the QUASAAR Marie Curie Network

Gas radon emission related to geodynamic activity on Mt. Etna

We report preliminary observations on possible correlations between anomalies of subsoil radon concentration and geodynamical events on Mt. Etna. In recent years several studies have been carried out on radon as a precursor of geophysical events, most of them performed either on tectonic or volcanic areas. The peculiarity of our investigation lies on the choice of the etnean region, in which tectonic and volcanic features are both present. In order to characterize Mt. Etna features by investigating radon gas in soil, two stations were located along the NE-SW direction on Mt. Etna. Each of the two stations is fitted with a radon detector, a 3D seismic station and a meteorological station. Differences in the radon concentration trend in the data from north and south flanks could be linked to different faulting mechanisms and then to different mechanisms of radon uprising. The increase in soil radon concentration could be related to both seismic and volcanic events

Indoor and soil radon measurements in the Hyblean Foreland (South-East Sicily)

Indoor radon behavior in two sites of SE Sicily was studied as a function of the soil radon concentration. The chosen locations were Ragusa and Modica towns, placed in the Hyblean Plateau (northern margin of the African Plate). Soil samples were analysed by gamma spectrometry to determine the amount of radionuclides. Indoor air and soil gas radon measurements were simultaneously performed in both sites using active detectors. Radon in soil was measured one meter deep. A positive correlation was obtained between indoor radon concentration and the soil gas concentration

Radiation measurements as tool for environmental and geophysics studies on volcano-tectonic areas

In the last years there has been an increasing concern about naturalradioactivity measurements both from the point of view of the environmental survey, especially for the human health protection, and of the geophysical-events investigation in volcanic areas and tectonic fault zones. We report on our activity in both these fields, in particular on the measurements of indoor radon concentration in a long-term passive monitoring in dwellings of the eastern region of Sicily. Because this region is characterized by high seismicity, besides the indoor radioactivity survey, in-soil radon measurements in the region (both volcanic and tectonic area) can provide a better insight and a valuable database for the study related to radon anomalies. A synthesis is reported of the results that we obtained, in the last years, in the volcanic and tectonic area of oriental Sicily both from indoor monitoring and from geophysical-events investigation

Indoor and soil radon measurements in the Hyblean Foreland (South-East Sicily)

Indoor radon behavior in two sites of SE Sicily was studied as a function of the soil radon concentration. The chosen locations were Ragusa and Modica towns, placed in the Hyblean Plateau (northern margin of the African Plate). Soil samples were analysed by gamma spectrometry to determine the amount of radionuclides. Indoor air and soil gas radon measurements were simultaneously performed in both sites using active detectors. Radon in soil was measured one meter deep. A positive correlation was obtained between indoor radon concentration and the soil gas concentration

10 ps timing with highly irradiated 3D trench silicon pixel sensors

In this paper the results of a beam test characterization campaign of 3D trench silicon pixel sensors are presented. A time resolution in the order of 10 ps was measured both for non-irradiated and irradiated sensors up to a fluence of $2.5 \cdot 10^{16}\,1\,MeV\, n_{eq}\,cm^{-2}$. This feature and a detection efficiency close to $99\%$ make this sensors one of the best candidates for 4D tracking detectors in High-Energy-Physics experiments.Comment: Prepared for submission to JINST, IWORID 202

SiPM-matrix readout of two-phase argon detectors using electroluminescence in the visible and near infrared range

Proportional electroluminescence (EL) in noble gases is used in two-phase detectors for dark matter searches to record (in the gas phase) the ionization signal induced by particle scattering in the liquid phase. The “standard” EL mechanism is considered to be due to noble gas excimer emission in the vacuum ultraviolet (VUV). In addition, there are two alternative mechanisms, producing light in the visible and near infrared (NIR) ranges. The first is due to bremsstrahlung of electrons scattered on neutral atoms (“neutral bremsstrahlung”, NBrS). The second, responsible for electron avalanche scintillation in the NIR at higher electric fields, is due to transitions between excited atomic states. In this work, we have for the first time demonstrated two alternative techniques of the optical readout of two-phase argon detectors, in the visible and NIR range, using a silicon photomultiplier matrix and electroluminescence due to either neutral bremsstrahlung or avalanche scintillation. The amplitude yield and position resolution were measured for these readout techniques, which allowed to assess the detection threshold for electron and nuclear recoils in two-phase argon detectors for dark matter searches. To the best of our knowledge, this is the first practical application of the NBrS effect in detection science

Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon

Large liquid argon detectors offer one of the best avenues for the detection of galactic weakly interacting massive particles (WIMPs) via their scattering on atomic nuclei. The liquid argon target allows exquisite discrimination between nuclear and electron recoil signals via pulse-shape discrimination of the scintillation signals. Atmospheric argon (AAr), however, has a naturally occurring radioactive isotope, 39Ar, a β emitter of cosmogenic origin. For large detectors, the atmospheric 39Ar activity poses pile-up concerns. The use of argon extracted from underground wells, deprived of 39Ar, is key to the physics potential of these experiments. The DarkSide-20k dark matter search experiment will operate a dual-phase time projection chamber with 50 tonnes of radio-pure underground argon (UAr), that was shown to be depleted of 39Ar with respect to AAr by a factor larger than 1400. Assessing the 39Ar content of the UAr during extraction is crucial for the success of DarkSide-20k, as well as for future experiments of the Global Argon Dark Matter Collaboration (GADMC). This will be carried out by the DArT in ArDM experiment, a small chamber made with extremely radio-pure materials that will be placed at the centre of the ArDM detector, in the Canfranc Underground Laboratory (LSC) in Spain. The ArDM LAr volume acts as an active veto for background radioactivity, mostly γ-rays from the ArDM detector materials and the surrounding rock. This article describes the DArT in ArDM project, including the chamber design and construction, and reviews the background required to achieve the expected performance of the detector

Preparatory work for C 3 line-list calculation.

The goal of this dissertation is to study the infrared absorption spectrum of the C 3 (carbon three) molecule. In particular, the aim is to investigate its ground electronic state up to 12:500 cm-1, as this affects the atmospheres of cool C-rich stars. The linear C 3 molecule shows very unusual properties for a linear molecule: a high degree of floppiness, no permanent dipole moment and a strong bentstretch interaction. Consequently, the C 3 spectrum presents particular features such as overtones, hot bands, and, as has been recently detected in Carbon stars and molecular clouds, a quite low fundamental bending frequency (63 cm-1) when in the ground electronic state. This dissertation aims to address each of these features. The first section discusses the context for this work: the stars. It provides a brief introduction about the Astrophysics related to this research project. A review at the recent literature is provided and the experimental results which provide the goal for the results of the theoretical work in the rest of the dissertation are set out. The second section introduces the C 3 molecule and outlines its properties. Previous C 3 studies are discussed and the theoretical approach used to study ro-vibrational spectra of triatomic molecules is set out. Preparatory tests and calculations are carried out to allow a theoretical reproduction of C 3 roto vibrational spectrum in the infrared region to be produced. The third part of the thesis expands on the nuclear motion calculations of section 2 and presents the results of the large scale calculations performed using the DVR3D suit programs written by Tennyson et al. [1]. This program allows the calculation of energy levels, wave-functions, expectation values and Einstein Coefficients. It takes as input the Potential Energy Surface (PES) and a Dipole Moment Surface (DMS) constructed a priori (in section 2) by solving the electronic problem within the Born-Oppenheimer's approximation. Because the quality of the PES sets the accuracy of the ro-vibrational calculations tests on different C 3 PESs and DMSs are performed. To reproduce accurate spectra of cool stars atmosphere in the temperature range of 2000 - 4000 K it was necessary perform calculations with high rotational quantum number. For this reason, tests with J>>0 were necessary to optimize the DVR3DRJZ parameters in order to guarantee a certain degree of accuracy and energy levels convergence. The results of these calculations and associated C 3 line-lists should be very useful to support the observations and model atmospheric studies. This work was generously supported by the QUASAAR Marie Curie Network.

The geodynamics of Mt. Etna volcano during and after the 1984 eruption

Data concerning M > 2.5 earthquakes that occurred at Mt. Etna volcano (Sicily, Italy) during the period April 15th - October 29th, 1984 are here presented and discussed. Only those events with reliable focal mechanisms (at least eight polarities) have been considered. Instrumental information comes from local seismic networks run by the University of Catania and the CNRS (Grenoble, France). The results obtained support the hypothesis that the seismicity and the volcanic activity at Mt. Etna are related to a complex stress field, due to the combined effects of the tectonics associated with the interaction between the African and Eurasian plates and the movement of magma into the crust. In particular, we hypothesize that the tectonic forces caused the end of the 1984 eruption, by means of a "locking mechanism"