Predissociation resonances and accurate ab initio calculations of dication HF2+

Highly accurate adiabatic potential curves of the 36 electronic states of the HF2+ dication by MRCI calculations. Panels (a), (b) and (c) correspond to the 16 singlet, 15 triplet and 4 quintet states, respectively. The nine bound states are highlighted and given in panel (d).

Dynamic Incremental Model (MDI) to forecast the SARS-CoV-2 pandemic stabilization period

Since the beginning of the year 2020, the world has been experiencing a COVID-19 pandemic, which challenges the public sector to make quick and efficient decisions, as the result is counted in lives. Thus, it is necessary to search for predictive models that support the decision and assist in the understanding of the behavior of the transmissions. In this context, the work aims to present a dynamic model for the daily increase in the number of deaths in order to determine a safety range capable of predicting a stabilization period for these deaths. For this, the model uses exponential and potential curves as limits for analyzing the behavior of the increment curve. The model proved to be efficient when compared to the actual data obtained so far.

High-Temperature Optical Spectra of Diatomic Molecules: Influence of the Avoided Level Crossing

In this study, we analyzed the light absorption by diatomic molecules or colliding atoms in a spectral region dominated by an avoided crossing of adiabatic state levels or crossing of the corresponding diabatic state levels. Our attention was focused on the low-resolution spectrum at a higher gas temperature under local thermodynamic equilibrium conditions. The absorption measurements of mixed vapors of potassium (≈80%) and cesium (≈20%) were made in the temperature range of 542–715 K and the infrared spectral range 900–1250 nm. In this area, the main spectral contributions were the broad A 1 Σ ( u ) + ( 0 ( u ) + ) − X 1 Σ ( g ) + ( 0 ( g ) + ) bands of K2, Cs2, and KCs molecules. There was a crossing of A 1 Σ ( u ) + ( 0 ( u ) + ) and b 3 Π ( u ) ( 0 ( u ) + ) state potential curves and the coupling of this state was due to the matrix element ⟨ A 1 Σ ( u ) + ( 0 ( u ) + ) | H s o | b 3 Π ( u ) ( 0 ( u ) + ) ⟩ of the spin–orbit interaction. Using data for relevant electronic potential curves and transition dipole moments existing in the literature, the spectra of the A 1 Σ ( u ) + ( 0 ( u ) + ) − X 1 Σ ( g ) + ( 0 ( g ) + ) molecular bands of K2, Cs2, and KCs molecules were calculated. Full quantum mechanical and semi-quantum coupled channel calculations were done and compared with their non-coherent adiabatic or diabatic approximations. Through the comparison of our theoretical and experimental spectra, we identified all observed spectral features and determined the atoms’ number density and gas temperature.

Photoionization of KCs Molecule: Origin of the Structured Continuum?

We report the experimental observation of photoionization bands of the KCs molecule in the deep ultraviolet spectral region between 200 and 420 nm. We discuss the origin of observed photoionization bands as stemming from the absorption from the ground state of the KCs molecule to the excited states of KCs+ molecule for which we used existing potential curves of the KCs+ molecule. An alternative explanation relies on the absorption from the ground state of the KCs molecule to the doubly excited states of the KCs** molecule, situated above the lowest molecular state of KCs+. The relevant potential curves of KCs** are not known yet, but all those KCs** potential curves are certainly autoionizing. However, these two photoionization pathways may interfere resulting in a special interference structured continuum, which is observed as complex bands.