Search results for "Synchrotron"
showing 10 items of 307 documents
First analysis of the ν3+ν5 combination band of SF6 observed at Doppler-limited resolution and effective model for the ν3+ν5-ν5 hot band
2018
Abstract Sulfur hexafluoride is a greenhouse gas with a long lifetime in the atmosphere and an important tracer for air mass circulation atmospheric models. The IR spectrum of this heavy species, however, features many hot bands at room temperature (at which only 30% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v 6 and v 5 = 1 vibrational states. Using a cryogenic long path cell with variable optical path length and temperatures regulated between 168 and 163 K, coupled to Synchrotron Radiation and a high resolution interferometer, Doppler-limited spectra of the very weak ν 3 + ν 5 band near 1450 cm−1 have been recorded. Low temperature…
Observation and analysis of the SF6 ν2+ν4−ν5 band: Improved parameters for the v5= 1 state
2016
Abstract In this paper, we present the high resolution analysis of the weak ν 2 + ν 4 - ν 5 band of SF6 around 735 cm−1. The spectra were recorded on the AILES Beamline at the SOLEIL Synchrotron facility using a cryogenic multipass cell coupled to a Bruker 125HR spectrometer with a maximum resolution of 0.00102 cm−1. For this band, we worked with 4 mbar of SF6 at a temperature of 223 ± 2 K. The optical path length was fixed to 141 m and the spectrum recorded with 0.001 cm−1 of resolution. A new, cold spectrum of the ν 2 + ν 4 band was also collected at 153 K, 15-m path length, and 0.0015 cm−1 resolution. The analysis was performed by using the Dijon group XTDS and SPVIEW software, based on…
Synchrotron-based Fourier transform spectra of the ν23 and ν24 IR bands of hexamethylenetetramine C6N4H12
2015
Abstract Hexamethylenetetramine (HMT), C6N4H12 is a spherical top with nine IR-active modes. Because of its relevance for astrophysics, we recorded the absorption spectra in the full range of its fundamental bands. In total, we detected eight fundamental bands and recently published the rotational analysis of the four most intense bands ( ν 19 , ν 20 , ν 21 , ν 22 ) located in the 1000–1500 cm−1 range as a support for astronomical searches (Pirali et al., 2014). While the CH stretch modes are unresolved broad features, in this article we report the analysis of the two remaining fundamental bands exhibiting rotationally resolved structures: ν 23 –GS and ν 24 –GS located at about 820 cm−1 and…
Galactic synchrotron emission from WIMPs at radio frequencies
2011
Dark matter annihilations in the Galactic halo inject relativistic electrons and positrons which in turn generate a synchrotron radiation when interacting with the galactic magnetic field. We calculate the synchrotron flux for various dark matter annihilation channels, masses, and astrophysical assumptions in the low-frequency range and compare our results with radio surveys from 22 MHz to 1420 MHz. We find that current observations are able to constrain particle dark matter with "thermal" annihilation cross-sections, i.e. (\sigma v) = 3 x 10^-26 cm^3/s, and masses M_DM < 10 GeV. We discuss the dependence of these bounds on the astrophysical assumptions, namely galactic dark matter distribu…
Neutrino Pair Synchrotron Radiation from Relativistic Electrons in Strong Magnetic Fields
1995
The emissivity for the neutrino pair synchrotron radiation in strong magnetic fields has been calculated both analytically and numerically for high densities and moderate temperatures, as can be found in neutron stars. Under these conditions, the electrons are relativistic and degenerate. We give here our results in terms of an universal function of a single variable. For two different regimes of the electron gas we present a simplified calculation and compare our results to those of Kaminker et al. Agreement is found for the classical region, where many Landau levels contribute to the emissivity , but some differences arise in the quantum regime. One finds that the emissivity for neutrino …
Cosmological radio emission induced by WIMP Dark Matter
2011
We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJa…
Jet stability and the generation of superluminal and stationary components
2001
We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component, instead of being ejected from the core. Their oblique nature should also result in distinc…
DEPFET based Instrumentation for the MIXS focal plane on BepiColombo
2009
BepiColombo, ESA's fifth cornerstone mission, is a planetary exploration mission to Mercury. On board of BepiColombo's Mercury Planetary Orbiter (MPO), the MIXS instrument will perform a complete X-ray fluorescence analysis of Mercury's crust with unprecedented spectral and spatial resolution. This is achieved by using a lightweight X-ray mirror system and by using of DEPFET based Macropixel devices as X-ray detectors. DEPFET based Macropixel detectors combine the advantages of the DEPFETs, like flexible readout modes, Fano-limited energy resolution and low power consumption, with the properties of the drift detectors, like arbitrary scalable pixel size and geometry. In addition, the excell…
Spin polarisation and dichroism in ARUPS from thin rare earth films
2001
Abstract In the present study, spin polarisation and dichroism were investigated in angular resolved VUV photoemission ARUPS from magnetised as well as paramagnetic rare earth surfaces. Thin Gd(0001) films were prepared epitaxially on W(110). The photoelectrons were excited by polarised synchrotron radiation from the BESSY I synchrotron radiation source. A SPLEED detector attached to an electron spectrometer mounted on a single axis goniometer was used for angular resolved spin analysis. The main part of this work focused on the characteristic surface state of Gd(0001) which shows a splitting, as previously observed by linear magnetic dichroism and spin polarised photoemission. The spin ana…
Laser cooling of relativistic heavy-ion beams for FAIR
2015
Laser cooling is a powerful technique to reduce the longitudinal momentum spread of stored relativistic ion beams. Based on successful experiments at the experimental storage ring at GSI in Darmstadt, of which we show some important results in this paper, we present our plans for laser cooling of relativistic ion beams in the future heavy-ion synchrotron SIS100 at the Facility for Antiproton and Ion Research in Darmstadt.