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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, De 1 satellite radio observations were conducted in the 1525-5925 Hz range during a pass over an ionospheric heating facility; the waves were detected during a 2-min period, and the measurements indicated pulse-stretching by a few hundred msec, in conjunction with spectral broadening of about 10 Hz.
Abstract: DE 1 satellite radio observations were conducted in the 1525-5925 Hz range during a pass over an ionospheric heating facility; the waves were detected during a 2-min period, and the measurements indicated pulse-stretching by a few hundred msec, in conjunction with spectral broadening of about 10 Hz. The observed signal delays and pulse distortion are not consistent with expectations assuming propagation in a smooth magnetosphere between the assumed 'polar electrojet antenna' in the ionospheric D/E region and the 11,000-km altitude of the satellite. Scattering by density irregularities is judged the likely sources of the spectral broadening and delays.
31 citations
TL;DR: It is concluded that spectral width and maximum frequency are best calculated using the finite beam-width model, and that ultrasound manufacturers could improve the variation in spectral broadening measured at different locations on a single machine by adjusting the aperture size to give a constant subtended angle and beam width.
Abstract: The purpose of the study was to compare measured spectral width and maximum frequency with that predicted from ray models of geometric spectral broadening. Zero and finite beam-width models were used. Spectral data were acquired from a string phantom using two commonly-used linear array systems. Beam width and Doppler aperture sizes were measured using a needle hydrophone. The results showed that the experimentally measured data agreed best with the finite beam-width model. The zero beam-width model was in error by up to 50% for calculated spectral width, and up to 10% for maximum frequency. It is concluded that spectral width and maximum frequency are best calculated using the finite beam-width model, and that ultrasound manufacturers could improve the variation in spectral broadening measured at different locations on a single machine by adjusting the aperture size to give a constant subtended angle and beam width.
31 citations
TL;DR: The novel theory of nonradiative decay of the intramolecular charge-transfer excited states is carried out for dyes and organic compounds of different nature, both for polar and nonpolar media.
Abstract: The fluctuations of orientation and induction interactions in solution and their impact on the broadening of absorption and fluorescence spectra are considered in terms of a bands-of-energy model. Also covered is the application of principles of thermodynamics and self-organization of systems for calculation of solvatochromic shift, among them a component owing to the work on electronic polarization of solvent at the instant of electronic transition in the solute. The findings on solvatochromic shift and spectral broadening open the way to the calculation of solvent effects on the rate constant of nonradiative transitions. As demonstrated herein for 15 fluorophores, the novel theory of nonradiative decay of the intramolecular charge-transfer excited states is carried out for dyes and organic compounds of different nature, both for polar and nonpolar media.
31 citations
TL;DR: A constant UV cutoff wavelength close to 400 nm was observed in the supercontinuum spectrum, indicating that intensity clamping still plays a role in tight focusing geometry.
Abstract: Supercontinuum generation in air using tightly focused femtosecond laser pulses was investigated experimentally Broadband white-light emission covering the whole visible spectral region was generated Spectral broadening extended only to the blue side of the fundamental frequency due to the phase modulation induced by the strong ionization of air Numerical simulation was also performed to confirm the spectral broadening mechanism A constant UV cutoff wavelength close to 400 nm was observed in the supercontinuum spectrum This phenomenon indicated that intensity clamping still plays a role in tight focusing geometry
30 citations
TL;DR: It is demonstrated that the CRD spectrometer with extremely high sensitivity is also very suitable for quantitative measurements including precise line profile studies in the near-infrared.
Abstract: A cavity ring-down (CRD) spectrometer is built with a continuous-wave Ti:sapphire ring laser. Using a pair of R∼0.999 95 high-reflective mirrors, the noise-equivalent minimum detectable absorption loss reaches 7×10−11/cm over the spectral range of 780–830 nm. A thermal-stabilized Fabry-Perot interferometer is applied to calibrate the CRD spectrum with an accuracy of 1×10−4 cm−1. The quantitative measurement is carried out for the line profile measurements of some overtone absorption lines of C2H2 near 787 nm. Doppler determined line shape has been observed with milli-Torr acetylene gas in the ring-down cavity. The instrumental line width is estimated from the line profile fitting to be <1×10−4 cm−1. It demonstrates that the CRD spectrometer with extremely high sensitivity is also very suitable for quantitative measurements including precise line profile studies in the near-infrared.
30 citations