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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: In this paper, a positron pulsing system for variable energy positron lifetime spectroscopy was constructed, which consists of a reflection type chopper, a sub-harmonic prebuncher, and a double harmonic buncher.
Abstract: A positron pulsing system has been constructed for variable energy positron lifetime spectroscopy. The system consists of a reflection type chopper, a sub-harmonic prebuncher, and a double harmonic buncher. By operating the system with an intense slow positron beam generated by an electron linac, positron lifetime spectra have been successfully measured in an extended time range of more than 45 ns with a good time resolution (250 ps). Furthermore, Doppler broadening profiles of annihilation radiations can be obtained simultaneously with the lifetime measurements.
144 citations
TL;DR: In this paper, a planar microcavity light emitting diodes with different device diameters were used to achieve a record external quantum efficiency of 20% for a 1.5 mm light emitting diode and a good correspondence was obtained when spectral broadening and photon recycling were taken into account.
Abstract: Results are presented on planar microcavity light emitting diodes with different device diameters. A record external quantum efficiency of 20% is achieved for a 1.5 mm light emitting diode. The strong dependence of the quantum efficiency on current density and device size are compared with theoretical results. A good correspondence is obtained when spectral broadening and photon recycling are taken into account.
141 citations
TL;DR: In this article, high-resolution spectroscopic measurements of H2O vapor in the 720-nm wavelength region were conducted to investigate the broadening and shifting of H 2O lines by air, nitrogen, oxygen, and argon over a wide range of pressures and temperatures.
141 citations
TL;DR: In this paper, the nonlinear propagation of ultrashort pulses in a microstructured fiber is experimentally investigated, and the output spectrum is made of a broad infrared supercontinuum coexisting with a sharp and very intense blue peak that takes up to 24% of the input power.
Abstract: The nonlinear propagation of ultrashort pulses in a microstructured fiber is experimentally investigated. By working around 800 nm, in the anomalous dispersion region, clear evidence of pulse break-up and soliton propagation is obtained. This is consistent with the recently suggested mechanism of spectral broadening based upon the fission of higher order solitons into red-shifted fundamental solitons and blue-shifted dispersion waves. When 190-fs pulses at high input intensities are used, the output spectrum is made of a broad infrared supercontinuum coexisting with a sharp and very intense blue peak that takes up to 24% of the input power. We tentatively propose an explanation of this effect by invoking pulse-trapping phenomena controlled by the group-velocity matching of infrared and visible pulses.
140 citations
TL;DR: In this paper, the effect of space charge on photoelectron spectroscopy from a surface using a pulsed and intense femtosecond light source has been investigated, focusing on a quantitative evaluation of the induced spectral broadening.
Abstract: In this paper, we present experimental results on the effect of space charging in photoelectron spectroscopy from a surface using a pulsed and intense femtosecond light source. We particularly focus on a quantitative evaluation of the induced spectral broadening. Our results are compared with analytic calculations based on energy conservation considerations as well as with experimental results from measurements using picosecond pulses for the excitation process. As a measure of space charge effects, we monitored the angular and energy distributions of the photoemission from the occupied Shockley surface state of Cu(111) as a function of the total number N of the photoemitted electrons per laser pulse. Our results show that spectral distortions exist for the entire laser fluence regime probed. The energetic broadening of the surface state peak can be fitted with remarkable accuracy by a N dependence, in agreement with the theoretical predictions and different from the experimental picosecond results, where...
140 citations