28 research outputs found
Laser-induced solid-solid phase transition in As under pressure: A theoretical prediction
In Arsenic a pressure-induced solid-solid phase transition from the A7 into
the simple cubic structure has been experimentally demonstrated [Beister et
al., Phys. Rev. B 41, 5535 (1990)]. In this paper we present calculations,
which predict that this phase transition can also be induced by an ultrashort
laser pulse in As under pressure. In addition, calculations for the
pressure-induced phase transition are presented. Using density functional
theory in the generalized gradient approximation, we found that the
pressure-induced phase transition takes place at 26.3 GPa and is accompanied by
a volume change "Delta V" = 0.5 bohr^3/atom. The laser-induced phase transition
is predicted for an applied pressure of 23.8 GPa and an absorbed laser energy
of 2.8 mRy/atom.Comment: 9 pages, 5 figures Changes to content To be published in New Journal
of Physics (accepted for publication
An Optical Atomic Clock Based on a Highly Charged Ion
Optical atomic clocks are the most accurate measurement devices ever
constructed and have found many applications in fundamental science and
technology. The use of highly charged ions (HCI) as a new class of references
for highest accuracy clocks and precision tests of fundamental physics has long
been motivated by their extreme atomic properties and reduced sensitivity to
perturbations from external electric and magnetic fields compared to singly
charged ions or neutral atoms. Here we present the first realisation of this
new class of clocks, based on an optical magnetic-dipole transition in
Ar. Its comprehensively evaluated systematic frequency uncertainty of
is comparable to that of many optical clocks in operation.
From clock comparisons we improve by eight and nine orders of magnitude upon
the uncertainties for the absolute transition frequency and isotope shift
(Ar vs. Ar), respectively. These measurements allow us to probe
the largely unexplored quantum electrodynamic nuclear recoil, presented as part
of improved calculations of the isotope shift which reduce the uncertainty of
previous theory by a factor of three. This work establishes forbidden optical
transitions in HCI as references for cutting-edge optical clocks and future
high-sensitivity searches for physics beyond the standard model.Comment: Main: 20 pages, 3 figures. Supplement: 19 pages, 2 figure
Guidelines for developing optical clocks with fractional frequency uncertainty
There has been tremendous progress in the performance of optical frequency
standards since the first proposals to carry out precision spectroscopy on
trapped, single ions in the 1970s. The estimated fractional frequency
uncertainty of today's leading optical standards is currently in the
range, approximately two orders of magnitude better than that of the best
caesium primary frequency standards. This exceptional accuracy and stability is
resulting in a growing number of research groups developing optical clocks.
While good review papers covering the topic already exist, more practical
guidelines are needed as a complement. The purpose of this document is
therefore to provide technical guidance for researchers starting in the field
of optical clocks. The target audience includes national metrology institutes
(NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD
students and postdocs entering the field. Another potential audience is
academic groups with experience in atomic physics and atom or ion trapping, but
with less experience of time and frequency metrology and optical clock
requirements. These guidelines have arisen from the scope of the EMPIR project
"Optical clocks with uncertainty" (OC18). Therefore, the
examples are from European laboratories even though similar work is carried out
all over the world. The goal of OC18 was to push the development of optical
clocks by improving each of the necessary subsystems: ultrastable lasers,
neutral-atom and single-ion traps, and interrogation techniques. This document
shares the knowledge acquired by the OC18 project consortium and gives
practical guidance on each of these aspects
Guidelines for developing optical clocks with 10-18 fractional frequency uncertainty
There has been tremendous progress in the performance of optical frequency standards since the first proposals to carry out precision spectroscopy on trapped, single ions in the 1970s. The estimated fractional frequency uncertainty of today's leading optical standards is currently in the 10â18 range, approximately two orders of magnitude better than that of the best caesium primary frequency standards. This exceptional accuracy and stability is resulting in a growing number of research groups developing optical clocks. While good review papers covering the topic already exist, more practical guidelines are needed as a complement. The purpose of this document is therefore to provide technical guidance for researchers starting in the field of optical clocks. The target audience includes national metrology institutes (NMIs) wanting to set up optical clocks (or subsystems thereof) and PhD students and postdocs entering the field. Another potential audience is academic groups with experience in atomic physics and atom or ion trapping, but with less experience of time and frequency metrology and optical clock requirements. These guidelines have arisen from the scope of the EMPIR project "Optical clocks with 1Ă10â18 uncertainty" (OC18). Therefore, the examples are from European laboratories even though similar work is carried out all over the world. The goal of OC18 was to push the development of optical clocks by improving each of the necessary subsystems: ultrastable lasers, neutral-atom and single-ion traps, and interrogation techniques. This document shares the knowledge acquired by the OC18 project consortium and gives practical guidance on each of these aspects.EU/Horizon2020/EMPIR/E