2 research outputs found
Detection of metastable electronic states by Penning trap mass spectrometry
State-of-the-art optical clocks achieve fractional precisions of
and below using ensembles of atoms in optical lattices or individual ions in
radio-frequency traps. Promising candidates for novel clocks are highly charged
ions (HCIs) and nuclear transitions, which are largely insensitive to external
perturbations and reach wavelengths beyond the optical range, now becoming
accessible to frequency combs. However, insufficiently accurate atomic
structure calculations still hinder the identification of suitable transitions
in HCIs. Here, we report on the discovery of a long-lived metastable electronic
state in a HCI by measuring the mass difference of the ground and the excited
state in Re, the first non-destructive, direct determination of an electronic
excitation energy. This result agrees with our advanced calculations, and we
confirmed them with an Os ion with the same electronic configuration. We used
the high-precision Penning-trap mass spectrometer PENTATRAP, unique in its
synchronous use of five individual traps for simultaneous mass measurements.
The cyclotron frequency ratio of the ion in the ground state to the
metastable state could be determined to a precision of , unprecedented in the heavy atom regime. With a lifetime of about 130
days, the potential soft x-ray frequency reference at has a linewidth of only , and one of the highest electronic quality factor
() ever seen in an experiment. Our low
uncertainty enables searching for more HCI soft x-ray clock transitions, needed
for promising precision studies of fundamental physics in a thus far unexplored
frontier
Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020
We show the distribution of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three genomic nomenclature systems to all sequence data from the World Health Organization European Region available until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation, compare the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2