3.10 Facultad de Física

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Browsing 3.10 Facultad de Física by Subject "09 Industria, innovación e infraestructura"

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    Anomalous Positron and Antiproton Cosmic Ray Flux in the Minimal Supersymmetric Standard Model Plus R-Parity Violation
    (2025) Ortega Gutiérrez, Gonzalo; Díaz Gutiérrez, Marco Aurelio; Pontificia Universidad Católica de Chile. Instituto de Física
    The Alpha Magnetic Spectrometer (AMS) located in the International Space Station, measured anomalous fluxes of positrons and antiprotons. The standard astronomical sources are not enough to describe the fluxes measured. We explain it with physics beyond the Standard Model: the Minimal Supersymmetric Standard Model plus R-Parity Violation. Gravitino, the graviton suṕerpartner, plays a fundamental role in our study because the different gravitino decay channels would contribute to the positron and antiproton fluxes measured by AMS. The main focus of our study is to find the best branching ratios associated with the decay channels, which adjust to AMS measurements, considering gravitino properties as its mass and lifetime.
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    Optical characterization of single molecules for quantum technologies
    (2025) Vera Castillo, Nicolás; Maze Ríos, Jerónimo; Pontificia Universidad Católica de Chile. Facultad de Física
    In this thesis, the optical properties of Vanadium Oxide Phthalocyanine (VOPc) molecules were studied using a home-built confocal microscope setup. Single VOPc molecules were successfully isolated and identified by their distinct diffraction-limited spots. Two sample preparation techniques were compared: spin coating and ion exchange. Spin coating produced less density of spots, while ion exchange resulted in more photostable spots.The emission spectra of the isolated spots were consistent with the known spectrum of VOPc, showing two peaks around 855 nm and 877 nm. The polarization response of the molecules indicated that they are randomly oriented in the sample. The lifetime of VOPc molecules was measured using time-correlated single photon counting (TCSPC), revealing an unexpected oscillatory behavior at high excitation powers, which disappeared at lower powers. This behavior suggests that the oscillation might be due to the laser's stability or noise. The lifetimes measured in an ensemble of VOPc were τ1 = 0.038 ns and τ2 = 0.221 ns for a power of 3.5 μW, and τ1 = 0.034 ns and τ2 = 0.084 ns. This power dependence on the excitation power is not the expected behavior as the lifetime should be a fixed characteristic of the molecule. Overall, the study provided valuable insights into the optical properties and isolation of VOPc molecules. Future work could focus on measuring the saturation curve of the fluorescence, confirming the presence of single molecules using second-order autocorrelation, and investigating the interaction of VOPc molecules with magnetic fields for potential applications in quantum technologies.
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    Single Molecules for Quantum Information and Metrology
    (2024) Escalante, Richard; Maze Ríos, Jerónimo; Pontificia Universidad Católica de Chile. Facultad de Física
    Single luminescent molecules provide a unique approach in the development of quantum technologies utilizing single photon sources. This includes quantum metrology by using a molecule’s sensitivity of its emission and magnetic properties to the local environment. In this thesis, we present our investigation of the optical properties of several different classes of luminescent molecules. We begin by providing some theoretical background of single quantum emitters as well as a brief description of the experimental methodologies and equipment. Next, we present an optical investigation of an ensemble of iron phthalocyanines molecules. This molecule possesses a ground state triplet, which is a desirable property for optically active spin qubits, but has a very weak optical emission. Diffraction limited spots displayed photo-instability in the form of blinking and irreversible bleaching. In ensemble form however, their optical stability allowed us to identify a possible Raman peak where we calculated the associated phonon frequency. Next, we present our single molecule study of vanadium phthalocyanine. This molecule has been documented as displaying very long spin coherence times even at room temperatures. We confirmed the presence of a single molecule by measuring the second order correlation function. Additionally, we looked at the intensity and spectral response as a function of the excitation laser polarization. The spectrum was fitted to a two Gaussian function, which may correspond to the two dipole transitions as suggested by theoretical calculations. Lastly, we looked at the optical properties of rare earth europium complexes known for having very sharp optical transitions in the emission spectrum, with each having varying levels of sensitivity to the local environment. Motivated by techniques to investigate non-radiative decay channels, we looked at the optical response of four different europium complexes under two 1 µs pulses of 515 nm laser separated by 1 µs. Each displayed a very different results and allowed us to identify the best candidates for single molecule studies. Finally, we looked at the emission spectrum as well as the optical response under a 6 µs long pulse using time-correlation single photon spectroscopy.