28 research outputs found
X-ray frequency combs from optically controlled resonance fluorescence
An x-ray pulse-shaping scheme is put forward for imprinting an optical
frequency comb onto the radiation emitted on a driven x-ray transition, thus
producing an x-ray frequency comb. A four-level system is used to describe the
level structure of N ions driven by narrow-bandwidth x rays, an optical
auxiliary laser, and an optical frequency comb. By including many-particle
enhancement of the emitted resonance fluorescence, a spectrum is predicted
consisting of equally spaced narrow lines which are centered on an x-ray
transition energy and separated by the same tooth spacing as the driving
optical frequency comb. Given a known x-ray reference frequency, our comb could
be employed to determine an unknown x-ray frequency. While relying on the
quality of the light fields used to drive the ensemble of ions, the model has
validity at energies from the 100 eV to the keV range.Comment: 11 pages, 2 figure
Astrophysical line diagnosis requires non-linear dynamical atomic modeling
Line intensities and oscillator strengths for the controversial 3C and 3D
astrophysically relevant lines in neonlike Fe ions are calculated. We
show that, for strong x-ray sources, the modeling of the spectral lines by a
peak with an area proportional to the oscillator strength is not sufficient and
non-linear dynamical effects have to be taken into account. Furthermore, a
large-scale configuration-interaction calculation of oscillator strengths is
performed with the inclusion of higher-order electron-correlation effects. The
dynamical effects give a possible resolution of discrepancies of theory and
experiment found by recent measurements, which motivates the use of
light-matter interaction models also valid for strong light fields in the
analysis and interpretation of astrophysical and laboratory spectra.Comment: 5 pages, 3 figure
Broadband high-resolution x-ray frequency combs
Optical frequency combs have had a remarkable impact on precision
spectroscopy. Enabling this technology in the x-ray domain is expected to
result in wide-ranging applications, such as stringent tests of astrophysical
models and quantum electrodynamics, a more sensitive search for the variability
of fundamental constants, and precision studies of nuclear structure.
Ultraprecise x-ray atomic clocks may also be envisaged. In this work, an x-ray
pulse-shaping method is put forward to generate a comb in the absorption
spectrum of an ultrashort high-frequency pulse. The method employs an
optical-frequency-comb laser, manipulating the system's dipole response to
imprint a comb on an excited transition with a high photon energy. The
described scheme provides higher comb frequencies and requires lower
optical-comb peak intensities than currently explored methods, preserves the
overall width of the optical comb, and may be implemented by presently
available x-ray technology
Worldwide tests of generic attractants, a promising tool for early detection of non-native cerambycid species
A large proportion of the insects which have invaded new regions and countries are emerging species, being found for the first time outside their native range. Being able to detect such species upon arrival at ports of entry before they establish in non-native countries is an urgent challenge. The deployment of traps baited with broad-spectrum semiochemical lures at ports-of-entry and other high-risk sites could be one such early detection tool. Rapid progress in the identification of semiochemicals for cerambycid beetles during the last 15 years has revealed that aggregation-sex pheromones and sex pheromones are often conserved at global levels for genera, tribes or subfamilies of the Cerambycidae. This possibly allows the development of generic attractants which attract multiple species simultaneously, especially when such pheromones are combined into blends. Here, we present the results of a worldwide field trial programme conducted during 2018-2021, using traps baited with a standardised 8-pheromone blend, usually com-plemented with plant volatiles. A total of 1308 traps were deployed at 302 sites covering simultaneously or sequentially 13 European countries, 10 Chinese provinces and some regions of the USA, Canada, Australia, Russia (Siberia) and the Caribbean (Martinique). We intended to test the following hypotheses: 1) if a species is regularly trapped in significant numbers by the blend on a continent, it increases the prob-ability that it can be detected when it arrives in other countries/continents and 2) if the blend exerts an effective, generic attraction to multiple species, it is likely that previously unknown and unexpected spe-cies can be captured due to the high degree of conservation of pheromone structures within related taxa. A total of 78,321 longhorned beetles were trapped, representing 376 species from eight subfamilies, with 84 species captured in numbers greater than 50 individuals. Captures comprised 60 tribes, with 10 tribes including more than nine species trapped on different continents. Some invasive species were captured in both the native and invaded continents. This demonstrates the potential of multipheromone lures as ef-fective tools for the detection of 'unexpected' cerambycid invaders, accidentally translocated outside their native ranges. Adding new pheromones with analogous well-conserved motifs is discussed, as well as the limitations of using such blends, especially for some cerambycid taxa which may be more attracted by the trap colour or other characteristics rather than to the chemical blend