Frederico Vasconcellos Prudente

We study the out-of-equilibrium dynamics of dipolar bosons and fermions after a sudden change in the interaction strength from zero to a finite repulsive value. We simulate the interaction quench on the initial state which is the ground state of harmonic potential with noninteracting bosons and fermions. We solve the time-dependent many-boson Schrödinger equation exactly using numerical methods. To understand the many-body dynamics we analyze several measures of many-body information entropy, monitoring their time evolution and assessing their dependence on interaction strength. We establish that for weak interaction quench the dynamics is statistics independent, both dipolar bosons and fermions do not relax, whereas it is significantly different for dipolar bosons from that of dipolar fermions in the stronger interaction quench. While dipolar bosons exhibit concurrent signature of relaxation in all entropy measures, dipolar fermions fail to relax, exhibiting modulated oscillation in all entropy dynamics. For dipolar bosons and larger interaction quench, the many-body information entropy measures dynamically approach the value predicted for the Gaussian orthogonal ensemble of random matrices, implying statistical relaxation and ergodicity. The entire relaxation process and signature of ergodicity are established by three unique features: dynamical delocalization in Hilbert space, violent orbital fragmentation, and saturation of all entropy measures to the maximum entropy states in the long-time dynamics. It highlights the importance of many-body effects with a possible exploration in quantum simulation with ultracold atoms.

An experimental and theoretical investigation of acetaldehyde’s photoabsorption and photoionization in the vacuum-ultraviolet energy range is presented. The absorption cross sections and the ionization efficiency were measured using a double-ion-chamber spectrometer in the 10.8–21.4 eV and 13.5–21.4 eV ranges, respectively. No previous reports of these quantities were found in the literature in this energy range. Photoionization and neutral-decay cross sections were derived from these results. Theoretical calculations were performed using the Padé approximant technique and the single-center partial-wave expansion method, which were applied to solve the Lippmann–Schwinger equation to obtain the asymmetry parameters and the photoionization cross sections for the seven outermost valence orbitals. The calculations were performed in the energy range from near-threshold to 35 eV at static-exchange and static-exchange-polarization levels of approximation. Our results are contextualized with recent studies on dissociative photoionization channels and high-resolution photoelectron spectra, enabling correlations with ionic fragmentation pathways. Our experimental and theoretical results were compared between each other and with previous results from the literature, exhibiting good agreement with the available data and providing a comprehensive data set essential for modeling photochemical processes in atmospheric and astrophysical environments.

We use the Shannon informational entropies as a tool to study the artificial helium atom, namely, two electrons confined in a quantum dot. We adopt configurations with spherical and cylindrical symmetries for the physical system of interest. Using the informational quantities, we analyze the effects of electronic confinement, we validate the entropic uncertainty relation, we identify that the Coulomb interaction potential between the electrons is no longer important for strong confinements, and we indicate/predict the avoided crossing phenomena. Finally, we carried out a density function analysis. When available, the results are compared with those in the literature.

We carried out a joint experimental and theoretical investigation of the interaction of vacuum-ultraviolet radiation with pyrrole molecules in the gas phase. A double-ion chamber spectrometer was used to measure the absolute photoabsorption cross-sections and the photoionization quantum yields from the ionization threshold to 21.5 eV using synchrotron radiation. Moreover, photoionization and neutral-decay cross-sections on an absolute scale were derived directly from the measured data. In addition, theoretical results of the photoionization cross-section (PICS) and asymmetric parameters were obtained from the ionization threshold to 50.0 eV considering all valence orbitals. These calculations were performed using the Padé approximant technique to solve the Lippmann–Schwinger equation at the static-exchange (SE) and static-exchange-polarization (SEP) levels of approximation. Comparisons are also made with the experimental and theoretical data available in the literature. We report, for the first time, experimental ionization efficiency, neutral decay cross-sections, theoretical photoionization cross-sections for each valence orbital, and several asymmetry parameters. In general, the results are consistent and in good agreement with the available data.