scispace - formally typeset
Search or ask a question
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
More filters
Journal ArticleDOI
TL;DR: In this article, an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with a Monte Carlo simulation framework was presented.
Abstract: We construct an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with a Monte Carlo simulation framework MONACO. Two torus geometries of smooth and clumpy cases are considered and compared. In order to reproduce a Compton shoulder accurately, MONACO includes not only free electron scattering but also bound electron scattering. Raman and Reyleigh scattering are also treated, and scattering cross sections dependent on chemical states of hydrogen and helium are included. Doppler broadening by turbulence velocity can be implemented. Our model gives consistent results with other available models, such as MYTorus, except for differences due to different physical parameters and assumptions. We studied the dependence on torus parameters for Compton shoulder, and found that a intensity ratio of Compton shoulder to line core mainly depends on the column density, inclination angle, and metal abundance. For instance, an increase of metal abundance makes the Compton shoulder relatively weak. Also, shape of Compton shoulder depends on the column density. Furthermore, these dependences become different between smooth and clumpy cases. Then, we discuss the possibility of ASTRO-H SXS spectroscopy of Compton shoulder in AGN reflection spectra.

48 citations

Journal ArticleDOI
TL;DR: In this article, a method is developed for calculating the cross section for line broadening in the limiting case in which important collisions may be considered to occur very rapidly with respect to the periods corresponding to the transitions in question.
Abstract: Collision broadening studies were made of optical double resonance lines in cadmium. The results indicate that the DELETE ABSTRACT 18574. A method is developed for calculating the cross section for line broadening in the limiting case in which important collisions may be considered to occur very rapidly with respect to the periods corresponding to the transitions in question. This method is essentially an extension of the familiar sudden approximation; reference is made throughout to the particular example of optical double resonance only for definiteness and because there are available experimental results for comparison with the theory. Assuming the impact model and considering the case when the energy levels in question are well resolved with respect to their width, an exact expression is found for resonant selfbroadening in the usual weak r-f field limit of interest in double resonance. For the case of very small oscillator strengths for the optical transition (intercombination lines), the resonant broadening becomes sufficiently small so that second-order, intermediate-state processes dominate, and approximations must be made to effect sums over intermediate states. Here the broadening is of the same sort as foreign gas broadening, and in many cases of interest, the approximations can be made in amore » sufficientiy realistic manner to obtain useful expressions for the broadening. It is shown that the resonant cross section and this secondorder cross section are not additive, but that the one that is larger dominates the total cross sections very strongly. The self-broadening and foreign gas broadening (by the noble gases) of double resonance lines in the group II metals and the self-broadening in the optical spectrum of helium are evaluated. In all cases the theoretical predictions are in good agreement with measurements. (auth)« less

48 citations

Journal ArticleDOI
24 May 2002
TL;DR: In this article, the spectral broadening of femtosecond Cr:forsterite laser pulses in tapered fibers was investigated. Butler et al. presented the results of their experiments devoted to the investigation of the femto-cond femtocond (F2F) laser pulses.
Abstract: Summary form only given. We present the results of our experiments devoted to the investigation of the spectral broadening of femtosecond Cr:forsterite laser pulses in tapered fibers. Unamplified Cr:forsterite laser pulses were coupled into a tapered fiber manufactured by tapering Corning SMF-28 standard telecommunications fibers with a core diameter of 9 /spl mu/m, a cutoff wavelength of 1250 nm, and a numerical aperture of 0.1.

47 citations

Journal ArticleDOI
TL;DR: This report reports on the first spectroscopic observation of the rotational Doppler shift associated with light beams carrying orbital angular momentum when the two incident Laguerre-Gaussian laser beams have opposite topological charges.
Abstract: We report on the first spectroscopic observation of the rotational Doppler shift associated with light beams carrying orbital angular momentum. The effect is evidenced as the broadening of a Hanle electromagnetically induced transparency coherence resonance on Rb vapor when the two incident Laguerre-Gaussian laser beams have opposite topological charges. The observations closely agree with theoretical predictions.

47 citations

Journal ArticleDOI
TL;DR: In this article, a least-squares fitting parametric estimation for VHF Doppler spectra was proposed to determine the distribution and air motions of raindrop size distribution and vertical air velocity.
Abstract: Raindrop size distribution and vertical air velocity are directly derived from VHF Doppler radar spectra in precipitation environments. As was first proposed by Wakasugi et al., we use a least-squares fitting parametric estimation for VHF Doppler spectra to determine the distribution and air motions. After discussing further the VHF Doppler spectrum method, especially the effects of spectral broadening mechanisms, the method is applied to Doppler spectra obtained during the seasonal rain front (Bai-u front) observation in Japan. Variations of vertical air velocity and distribution parameters are discussed, based on this longer period dataset.

47 citations


Network Information
Related Topics (5)
Scattering
152.3K papers, 3M citations
84% related
Excited state
102.2K papers, 2.2M citations
84% related
Laser
353.1K papers, 4.3M citations
83% related
Magnetic field
167.5K papers, 2.3M citations
82% related
Silicon
196K papers, 3M citations
81% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202331
202290
2021122
2020134
2019128
2018122