61 research outputs found
Precision measurement of the isotopic shift in calcium ions using photon recoil spectroscopy
[no abstract
Efficient sympathetic motional ground-state cooling of a molecular ion
Cold molecular ions are promising candidates in various fields ranging from
precision spectroscopy and test of fundamental physics to ultra-cold chemistry.
Control of internal and external degrees of freedom is a prerequisite for many
of these applications. Motional ground state cooling represents the starting
point for quantum logic-assisted internal state preparation, detection, and
spectroscopy protocols. Robust and fast cooling is crucial to maximize the
fraction of time available for the actual experiment. We optimize the cooling
rate of ground state cooling schemes for single ions and
sympathetic ground state cooling of . In particular, we
show that robust cooling is achieved by combining pulsed Raman sideband cooling
with continuous quench cooling. Furthermore, we experimentally demonstrate an
efficient strategy for ground state cooling outside the Lamb-Dicke regime.Comment: 11 pages, 11 figure
Detection of motional ground state population of a trapped ion using delayed pulses
Efficient preparation and detection of the motional state of trapped ions is
important in many experiments ranging from quantum computation to precision
spectroscopy. We investigate the stimulated Raman adiabatic passage (STIRAP)
technique for the manipulation of motional states in a trapped ion system. The
presented technique uses a Raman coupling between two hyperfine ground states
in Mg, implemented with delayed pulses, which removes a single
phonon independent of the initial motional state. We show that for a thermal
state the STIRAP population transfer is more efficient than a stimulated Raman
Rabi pulse on a motional sideband. In contrast to previous implementations, a
large detuning of more than 200 times the natural linewidth of the transition
is used. This approach renders STIRAP suitable for atoms in which resonant
laser fields would populate fluorescing excited states and thus impede the
STIRAP process. We use the technique to measure the wavefunction overlap of
excited motional states with the motional ground state. This is an important
application for photon recoil spectroscopy and other force sensing applications
that utilize the high sensitivity of the motional state of trapped ions to
external fields. Furthermore, a determination of the ground state population
enables a simple measurement of the ion's temperature.Comment: 17 pages, 7 figure
Precision isotope shift measurements in Ca using highly sensitive detection schemes
We demonstrate an efficient high-precision optical spectroscopy technique for
single trapped ions with non-closed transitions. In a double-shelving
technique, the absorption of a single photon is first amplified to several
phonons of a normal motional mode shared with a co-trapped cooling ion of a
different species, before being further amplified to thousands of fluorescence
photons emitted by the cooling ion using the standard electron shelving
technique. We employ this extension of the photon recoil spectroscopy technique
to perform the first high precision absolute frequency measurement of the
D P transition in Ca,
resulting in a transition frequency of kHz.
Furthermore, we determine the isotope shift of this transition and the
S P transition for Ca,
Ca and Ca ions relative to Ca with an
accuracy below 100 kHz. Improved field and mass shift constants of these
transitions as well as changes in mean square nuclear charge radii are
extracted from this high resolution data
Multispectral LIF-Based Standoff Detection System for the Classification of CBE Hazards by Spectral and Temporal Features
Laser-induced fluorescence (LIF) is a well-established technique for monitoring chemical
processes and for the standoff detection of biological substances because of its simple technical
implementation and high sensitivity. Frequently, standoff LIF spectra from large molecules and
bio-agents are only slightly structured and a gain of deeper information, such as classification,
let alone identification, might become challenging. Improving the LIF technology by recording
spectral and additionally time-resolved fluorescence emission, a significant gain of information can
be achieved. This work presents results from a LIF based detection system and an analysis of the
influence of time-resolved data on the classification accuracy. A multi-wavelength sub-nanosecond
laser source is used to acquire spectral and time-resolved data from a standoff distance of 3.5 m.
The data set contains data from seven different bacterial species and six types of oil. Classification is
performed with a decision tree algorithm separately for spectral data, time-resolved data and the
combination of both. The first findings show a valuable contribution of time-resolved fluorescence
data to the classification of the investigated chemical and biological agents to their species level.
Temporal and spectral data have been proven as partly complementary. The classification accuracy is
increased from 86% for spectral data only to more than 92%
Compact setup for standoff laser induced breakdown spectroscopy of radioactive material
Radioactive materials present a major threat and can cause severe direct and long term injuries to humans as experienced i.e. in the
Fukushima and Chernobyl nuclear plant catastrophes. Furthermore, intended use of radiological dispersal devices may spread
radioactive materials over large areas. Detecting these hazards and investigating the status of contaminated areas a remote standoff
determination of nuclear fission products would serve as a helpful tool for first responders and damage control teams. Laser induced
breakdown spectroscopy (LIBS) offers a unique possibility for the identification of nuclear fission products and can be able to
distinguish different isotopes of the same species. Within this scope and based on experiences with a high power / long distance (>
100 m) LIBS setup a compact and low power setup is presented. The compactness allows for handheld operation as well as mounted
on a small robot or on an unmanned aerial vehicle (UAV) an advanced setup could be controlled remotely and would be able to
safely determine radioactive materials
Precision spectroscopy by photon-recoil signal amplification
Precision spectroscopy of atomic and molecular ions offers a window to new
physics, but is typically limited to species with a cycling transition for
laser cooling and detection. Quantum logic spectroscopy has overcome this
limitation for species with long-lived excited states. Here, we extend quantum
logic spectroscopy to fast, dipole-allowed transitions and apply it to perform
an absolute frequency measurement. We detect the absorption of photons by the
spectroscopically investigated ion through the photon recoil imparted on a
co-trapped ion of a different species, on which we can perform efficient
quantum logic detection techniques. This amplifies the recoil signal from a few
absorbed photons to thousands of fluorescence photons. We resolve the line
center of a dipole-allowed transition in 40Ca+ to 1/300 of its observed
linewidth, rendering this measurement one of the most accurate of a broad
transition. The simplicity and versatility of this approach enables
spectroscopy of many previously inaccessible species.Comment: 25 pages, 6 figures, 1 table, updated supplementary information,
fixed typo
Recent trends in stream macroinvertebrates: warm-adapted and pesticide-tolerant taxa increase in richness
Recently, a plethora of studies reporting insect declines has been published. Even though the common theme is decreasing insect richness, positive trends have also been documented. Here, we analysed nationwide, systematic monitoring data on aquatic insect richness collected at 438 sites in Switzerland from 2010 to 2019. In addition to taxonomic richness, we grouped taxa in accordance with their ecological preferences and functional traits to gain a better understanding of trends and possible underlying mechanisms. We found that in general, richness of aquatic insects remained stable or increased with time. Warm-adapted taxa, common feeding guilds and pesticide-tolerant taxa showed increasing patterns while cold-adapted, rarer feeding guilds and pesticide-sensitive taxa displayed stable trends. Both climate and land-use-related factors were the most important explanatory variables for the patterns of aquatic insect richness. Although our data cover the last decade only, our results suggest that recent developments in insect richness are context-dependent and affect functional groups differently. However, longer investigations and a good understanding of the baseline are important to reveal if the increase in temperature- and pesticide-tolerant species will lead to a decrease in specialized species and a homogenization of biotic communities in the long term
Quantitative determination of hazardous substances in aerosols by light scattering and machine learning with the example of Cr(VI) in electroplating processes
Regulations of safety usage of hazardous substances impose companies to monitor their emissions. A novel approach is presented to determine the mass concentration of Cr(VI) in exhaust air based on angular light scattering combined with machine learning algorithm
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