Impact of buffer gas quenching on the S-1(0) -> P-1(1) ground-state atomic transition in nobelium

International audienceUsing the sensitive Radiation Detected Resonance Ionization Spectroscopy (RADRIS) techniquean optical transition in neutral nobelium (No, Z = 102) was identified. A remnant signal when delaying the ionizing laser indicated the influence of a strong buffer gas induced de-excitation of the optically populated level. A subsequent investigation of the chemical homologue, ytterbium (Yb, Z = 70), enabled a detailed study of the atomic levels involved in this process, leading to the development of a rate equation model. This paves the way for characterizing resonance ionization spectroscopy (RIS) schemes used in the studyof nobelium and beyond, where atomic properties are currently unknown

Molecular dynamics and phase field simulations of droplets on surfaces with wettability gradient

To understand how the motion of a droplet on a surface can be controlled by wettability gradients is interesting in a variety of technical applications. Phase field (PF) models can be used to study such scenarios but their application requires suitable models of the properties of the interacting phases: vapor, liquid, and solid. In this work, the PF simulations are linked to molecular models by using an equation of state as well as a correlation for the viscosity, that are both consistent with results determined by molecular dynamics (MD) simulations. The motion of a nanoscale droplet on a surface with a wettability gradient is studied both by MD simulations and PF simulations and the results are compared. In both methods, the wettability gradient is solely determined by the surface tensions of the liquid–vapor, solid–liquid, and solid–vapor interfaces. Simulations are conducted for two different profiles of the wettability and at two different temperatures. The qualitative and the quantitative behavior such as the shape of the droplet and the velocity of the motion are in good agreement. This validates the PF model for the determination of nanoscale phenomena, and enables an efficient investigation of nanoscale as well as larger scenarios. ⃝c 2019 Elsevier B.V. All rights reserved

Atom-at-a-time laser resonance ionization spectroscopy of nobelium

Optical spectroscopy of a primordial isotope has traditionally formed the basis for understanding the atomic structure of an element. Such studies have been conducted for most elements1 and theoretical modelling can be performed to high precision2,3, taking into account relativistic effects that scale approximately as the square of the atomic number. However, for the transfermium elements (those with atomic numbers greater than 100), the atomic structure is experimentally unknown. These radioactive elements are produced in nuclear fusion reactions at rates of only a few atoms per second at most and must be studied immediately following their production4, which has so far precluded their optical spectroscopy. Here we report laser resonance ionization spectroscopy of nobelium (No; atomic number 102) in single-atom-at-a-time quantities, in which we identify the ground-state transition 1S0 → 1P1. By combining this result with data from an observed Rydberg series, we obtain an upper limit for the ionization potential of nobelium. These accurate results from direct laser excitations of outer-shell electrons cannot be achieved using state-of-the-art relativistic manybody calculations5–8 that include quantum electrodynamic effects, owing to large uncertainties in the modelled transition energies of the complex systems under consideration. Our work opens the door to high-precision measurements of various atomic and nuclear properties of elements heavier than nobelium, and motivates future theoretical work. Since the establishmentstatus: publishe