arXiv subjects

L. F. Pašteka

Publications and source records attributed to L. F. Pašteka.

4 recordsLinked to original sources

arXiv2026

Ab Initio Calculations of the Static and Dynamic Polarizability of BaOH

We present high-precision ab initio calculations of the static and dynamic polarizability of the barium monohydroxide ($^{138}$BaOH) molecule, using relativistic coupled-cluster theory. By thoroughly investigating the dependence of the calculated polarizabilities on computational parameters (basis set size, treatment of relativity, level of treatment of electron correlation, and vibrational corrections), a procedure to determine uncertainties is constructed and applied. The dipole moment of BaOH is also calculated and compared to experiment, confirming the accuracy of the predicted polarizabilities. The static and dynamic ($λ=1064\;\text{nm}$) polarizability was calculated for both the ground state and the (010) vibrational bending mode, the latter state being particularly interesting for a wide range of quantum experiments. The ground state static polarizabilities were calculated to be 200.8(24) a.u. and 297(5) a.u. for the parallel and perpendicular components respectively.

physics.chem-ph↗

arXiv2025

Relativistic atomic structure calculations in support of spectroscopy

Theory can provide important support at all the stages of spectroscopic experiments, from planning the measurements to the interpretation of the results. Such support is particularly valuable for the challenging experiments on heavy, unstable, and superheavy elements and for precision measurements aimed at testing the Standard Model of particle physics. To be reliable and useful in experimental context, theoretical predictions should be based on high-accuracy calculations. For heavy elements, such calculations must treat both relativistic effects and electron correlation on the highest possible level. Relativistic coupled cluster is considered one of the most powerful methods for accurate calculations on heavy many-electron atoms and molecules. This approach is highly accurate and versatile and can be used to obtain energies and a variety of atomic and molecular properties. Furthermore, its robust and transparent formulation allows for systematic improvement of the accuracy of the calculated results and for assigning uncertainties on theoretical values. The Fock-space coupled cluster (FSCC) variant of this method is particularly useful in the context of spectroscopic measurements as it provides access to atomic spectra and properties of the excited states. In this review, we present in detail the relativistic coupled cluster approach and its FSCC variant. We provide a description of the computational procedure used for accurate calculations and for assigning uncertainties. Outstanding recent examples of application to atomic properties, focusing on the experimental context are presented. Finally, we provide a brief discussion of the perspectives for future developments and applications of the CC approach.

physics.atom-ph↗

arXiv2024

Pinning down electron correlations in RaF via spectroscopy of excited states and high-accuracy relativistic quantum chemistry

We report the spectroscopy of the 14 lowest excited electronic states in the radioactive molecule radium monofluoride (RaF). The observed excitation energies are compared with fully relativistic state-of-the-art Fock-space coupled cluster (FS-RCC) calculations, which achieve an agreement of >=99.64% (within ~12 meV) with experiment for all states. Guided by theory, a firm assignment of the angular momentum and term symbol is made for 10 states and a tentative assignment for 4 states. The role of high-order electron correlation and quantum electrodynamics effects in the excitation energy of excited states is studied, found to be important for all states. Establishing the simultaneous accuracy and precision of calculations is an important step for research at the intersection of particle, nuclear, and chemical physics, including searches of physics beyond the Standard Model, for which RaF is a promising probe.

physics.atom-ph↗

arXiv2024

Ionization potential of radium monofluoride

The ionization potential (IP) of radium monofluoride (RaF) was measured to be 4.969(2)[10] eV, revealing a relativistic enhancement in the series of alkaline earth monofluorides. The results are in agreement with a relativistic coupled-cluster prediction of 4.969[7] eV, incorporating up to quantum electrodynamics corrections. Using the same computational methodology, an improved calculation for the dissociation energy ($D_{0}$) of 5.54[5] eV is presented. This confirms that radium monofluoride joins the small group of diatomic molecules for which $D_{0}>\mathrm{IP}$, paving the way for precision control and interrogation of its Rydberg states.

physics.atom-ph↗