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Doppler broadening
About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.
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TL;DR: The UV spectrum of the 6(1)0 S1 <-- S0 vibronic transition of benzene, located at 259 nm, was recorded by means of a combination of a cw laser doubling unit and a molecular beam apparatus and general agreement with IR-band investigations was found.
41 citations
15 Nov 2011-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a new and unique setup for positron annihilation spectroscopy has been established and optimized at the superconducting linear electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf (Germany).
Abstract: A new and unique setup for Positron Annihilation Spectroscopy has been established and optimized at the superconducting linear electron accelerator ELBE at Helmholtz-Zentrum Dresden-Rossendorf (Germany). The intense, pulsed (26 MHz) photon source (bremsstrahlung with energies up to 16 MeV) is used to generate positrons by means of pair production throughout the entire sample volume. Due to the very short gamma bunches (< 5 ps temporal length), the facility for Gamma-induced Positron Spectroscopy (GiPS) is suitable for positron lifetime spectroscopy using the accelerator’s radiofrequency as time reference. Positron lifetime and Doppler broadening Spectroscopy are employed by a coincident measurement (Age–Momentum Correlation) of the time-of-arrival and energy of the annihilation photons which in turn significantly reduces the background of scattered photons resulting in spectra with high signal to background ratios. Simulations of the setup using the GEANT4 framework have been performed to yield optimum positron generation rates for various sample materials and improved background conditions.
41 citations
41 citations
TL;DR: In this paper, the authors implemented a Doppler processing technique that uses a data acquisition system developed for pulsed doppler radar for obtaining the complete spectrum of radial velocities of both precipitation particles and refractive-index fluctuations in the optically clear air.
Abstract: A microwave FM-CW radar can obtain the complete spectrum of radial velocities of both precipitation particles and refractive-index fluctuations in the optically clear air. Heretofore the extraction of the Doppler spectrum from this type of radar was believed to be a formidable, if not impossible, task. We have implemented a Doppler processing technique that uses a data acquisition system developed for pulsed Doppler radar. We present Doppler spectra obtained with a zenith-pointing FM-CW radar that demonstrate this new capability. In addition to the strong refractive-index layers observed by the FM-CW radar in the optically clear air, there is evidence that scattering from a background continuum of Cn² can be detected when a Doppler operating mode is employed.
41 citations
TL;DR: The combination of high temporal resolution and dynamic range in the measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.
Abstract: We present high resolution measurements of the ultrafast temporal dynamics of the critical surface in moderately overdense, hot plasma by using two-color, pump-probe Doppler spectrometry. Our measurements clearly capture the initial inward motion of the plasma inside the critical surface of the pump laser which is followed by outward expansion. The measured instantaneous velocity and acceleration profiles are very well reproduced by a hybrid simulation that uses a 1D electromagnetic particle-in-cell simulation for the initial evolution and a hydrodynamics simulation for the later times. The combination of high temporal resolution and dynamic range in our measurements clearly provides quantitative unraveling of the dynamics in this important region, enabling this as a powerful technique to obtain ultrafast snapshots of plasma density and temperature profiles for providing benchmarks for simulations.
41 citations