35 research outputs found
Accurate theoretical determination of the ionization potentials of CaF, SrF, and BaF
We present a comprehensive theoretical study of the ionization potentials of
the MF (M= Ca, Sr, Ba) molecules using the state-of-the-art relativistic
coupled cluster approach with single, double, and perturbative triple
excitations (CCSD(T)). We have further corrected our results for the higher
order excitations (up to full triples) and the QED self energy and vacuum
polarisation contributions. We have performed an extensive investigation of the
effect of the various computational parameters on the calculated ionisation
potentials, which allowed us to assign realistic uncertainties on our
predictions. For CaF and BaF, where precise experiments are available, our
predictions are in excellent agreement with the measured values. In case of
SrF, we provide a new accurate prediction of the ionisation potential that
deviates from the available experimental data, motivating further experimental
investigations.Comment: 7 pages, before paper submission (references will be added
additionally
Pinning down electron correlations in RaF via spectroscopy of excited states
We report the spectroscopy of 11 electronic states in the radioactive
molecule radium monofluoride (RaF). The observed excitation energies are
compared with state-of-the-art relativistic Fock-space coupled cluster (FS-RCC)
calculations, which achieve an agreement of >99.71% (within ~8 meV) for all
states. High-order electron correlation and quantum electrodynamics corrections
are found to be important at all energies. Establishing the accuracy of
calculations is an important step towards high-precision studies of these
molecules, which are proposed for sensitive searches of physics beyond the
Standard Model.Comment: Submitted for publicatio
Precision spectroscopy of fast, hot, exotic isotopes using machine-learning-assisted event-by-event Doppler correction
We propose an experimental scheme for performing sensitive, high-precision laser spectroscopy studies on fast exotic isotopes. By inducing a stepwise resonant ionization of the atoms traveling inside an electric field and subsequently detecting the ion and the corresponding electron, time-, and position-sensitive measurements of the resulting particles can be performed. Using a mixture density network, we can leverage this information to predict the initial energy of individual atoms and thus apply a Doppler correction of the observed transition frequencies on an event-by-event basis. We conduct numerical simulations of the proposed experimental scheme and show that kHz-level uncertainties can be achieved for ion beams produced at extreme temperatures (>10^{8}Â K), with energy spreads as large as 10 keV and nonuniform velocity distributions. The ability to perform in-flight spectroscopy, directly on highly energetic beams, offers unique opportunities to study short-lived isotopes with lifetimes in the millisecond range and below, produced in low quantities, in hot and highly contaminated environments, without the need for cooling techniques. Such species are of marked interest for nuclear structure, astrophysics, and new physics searches
Local photoionization feedback effects on galaxies
We implement an optically thin approximation for the effects of the local radiation field from stars and hot gas on the gas heating and cooling in the N-body SPH code GASOLINE2. We resimulate three galaxies from the NIHAO project: one dwarf, one Milky Way-like and one massive spiral, and study what are the local radiation field effects on various galaxy properties. We also study the effects of varying the Ultra Violet Background (UVB) model, by running the same galaxies with two different UVBs. Galaxy properties at z = 0 like stellar mass, stellar effective mass radius, HI mass, and radial extent of the HI disc, show significant changes between the models with and without the local radiation field, and smaller differences between the two UVB models. The intrinsic effect of the local radiation field through cosmic time is to increase the equilibrium temperature at the interface between the galaxies and their circumgalactic media (CGM), moving this boundary inwards, while leaving relatively unchanged the gas inflow rate. Consequently, the temperature of the inflow increases when considering the local radiation sources. This temperature increase is a function of total galaxy mass, with a median CGM temperature difference of one order of magnitude for the massive spiral. The local radiation field suppresses the stellar mass growth by 20 per cent by z = 0 for all three galaxies, while the HI mass is roughly halfed. The differences in the gas phase diagrams, significantly impact the HI column densities, shifting their peaks in the distributions towards lower NHI
Local photoionization feedback effects on galaxies
We implement an optically thin approximation for the effects of the local radiation field from stars and hot gas on the gas heating and cooling in the N-body smoothed particle hydrodynamics code gasoline2. We resimulate three galaxies from the NIHAO project: one dwarf, one Milky Way-like, and one massive spiral, and study what are the local radiation field effects on various galaxy properties. We also study the effects of varying the ultraviolet background (UVB) model, by running the same galaxies with two different UVBs. Galaxy properties at z = 0 like stellar mass, stellar effective mass radius, H i mass, and radial extent of the H i disc show significant changes between the models with and without the local radiation field, and smaller differences between the two UVB models. The intrinsic effect of the local radiation field through cosmic time is to increase the equilibrium temperature at the interface between the galaxies and their circumgalactic media (CGM), moving this boundary inwards, while leaving relatively unchanged the gas inflow rate. Consequently, the temperature of the inflow increases when considering the local radiation sources. This temperature increase is a function of total galaxy mass, with a median CGM temperature difference of one order of magnitude for the massive spiral. The local radiation field suppresses the stellar mass growth by 20 per cent by z = 0 for all three galaxies, while the H i mass is roughly halved. The differences in the gas phase diagrams, significantly impact the H i column densities, shifting their peaks in the distributions towards lower NH i