Topic
Doppler broadening
About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.
Papers published on a yearly basis
Papers
More filters
••
TL;DR: In this paper, a method for calculating the momentum density of positron-electron pairs in materials, which can be accurately measured, in a wide momentum range, by means of coincidence Doppler broadening (CDB), is presented, based on the two-component density-functional theory within the local density approximation.
Abstract: We report a first-principles method for calculating the momentum density of positron-electron pairs in materials, which can be accurately measured, in a wide momentum range, by means of coincidence Doppler broadening (CDB) of positron annihilation radiation. The calculation is based on the two-component density-functional theory within the local-density approximation. The electron and positron wave functions are calculated by means of the full-potential linearized-augmented-plane-wave method with use of semicore orbitals and of the pure plane-wave method, respectively. This hybrid basis set accurately determines the wave functions of core and valence electrons and is free from any shape or symmetry assumption for the positron wave function. The method is applied to two typical systems. i.e., Al and graphite having isotropic and anisotropic positron densities, respectively. The calculations agree well with experiments over the entire measurable momentum region. Especially, the calculations well reproduce the anisotropic high-momentum CDB tails of graphite, which originate from the quasi-two-dimensionally distributed positron. This reproduction suggests that the present method is applicable for a variety of materials.
26 citations
••
TL;DR: Shape, Intensity and Pressure Broadening of the 253 millimetre Wave-Length Oxygen Absorption Line (WLSO) as discussed by the authors was proposed for the first time.
Abstract: Shape, Intensity and Pressure Broadening of the 253-Millimetre Wave-Length Oxygen Absorption Line
26 citations
••
TL;DR: In this article, a scanning spectrometer comprising a large, high resolution Fabry-Perot etalon, a small, low resolution etalon and an interference filter was used for the recording of atomic spectral line emissions from the daytime upper atmosphere.
26 citations
••
TL;DR: In this article, the authors present the results of a comprehensive analytical and numerical study of ultrawide spectral broadening and compression of isolated extremely short visible, uv-vuv and middle infrared (MIR) pulses by high-order stimulated Raman scattering in hollow waveguides.
Abstract: We present the results of a comprehensive analytical and numerical study of ultrawide spectral broadening and compression of isolated extremely short visible, uv-vuv and middle infrared (MIR) pulses by high-order stimulated Raman scattering in hollow waveguides. Spectral and temporal characteristics of the output pulses and the mechanism of pulse compression using dispersion of the gas filling and output glass window are investigated without the slowly varying envelope approximation. Physical limitations due to phase mismatch, velocity walk off, and pump-pulse depletion as well as improvements through the use of pump-pulse sequences and dispersion control are studied. It is shown that phase-locked pulses as short as $\ensuremath{\sim}2\mathrm{fs}$ in the visible and uv-vuv, and 6.5 fs in the MIR can be generated by coherent scattering in impulsively excited Raman media without the necessity of external phase control. Using pump-pulse sequences, shortest durations in the range of about 1 fs for visible and uv-vuv probe pulses are predicted.
26 citations
••
TL;DR: In this paper, the Boltzmann constant was measured using the Doppler broadening technique on ammonia using a phase-stabilized quantum cascade laser and a linehape analysis based on a refined physical model.
Abstract: We report on our ongoing effort to measure the Boltzmann constant, k B , using the Doppler broadening technique on ammonia. This paper presents some of the improvements made to the mid-infrared spectrometer including the use of a phase-stabilized quantum cascade laser, a lineshape analysis based on a refined physical model and an improved fitting program 2 increasing the confidence in our estimates of the relevant molecular parameters, and a first evaluation of the saturation parameter and its impact on the measurement of k B. A summary of the systematic effects contributing to the measurement is given and the optimal experimental conditions for mitigating those effects in order to reach a competitive measurement of k B at a part per million accuracy level are outlined.
26 citations