Doppler broadening

About: Doppler broadening is a research topic. Over the lifetime, 5509 publications have been published within this topic receiving 92552 citations.

A critical study of ultrasound Doppler spectral analysis for detecting carotid disease

Abstract: The results of in vitro and in vivo studies to determine the application and limitations of frequency analysis for CW Doppler ultrasound assessment of carotid stenoses are reported. In the in vitro study, the peak Doppler frequency and a new spectral broadening index were determined proximal to, at, and distal to axisymmetric and asymmetrical model stenoses. Good correlations with percent area stenoses were found. In the clinical study, 162 cases were examined using a 4 MHz Doppler system and by standard four-vessel arteriography. Peak frequencies of greater than 3.8 KHz were diagnostic of internal carotid stenoses of 3.2 mm minimum lumen diameter or less, with a sensitivity of 92% and a specificity of 94%. Spectral broadening, evaluated by subjective grading, yielded similar results.

Enhanced nonlinear magneto-optical rotation in cold atoms: A theoretical study.

Abstract: We theoretically investigate magneto-optical rotation (MOR) of a linearly polarized probe field in the four-level N-type cold atoms. By applying a static magnetic field and a weak coupling field, it is shown that the birefringence enhancement is induced in the system. Moreover, we show that the static magnetic field has a major role in switching the dichroism to enhanced birefringence in the system. We also obtain a large intensity for the output field with nearly perpendicular MOR angle by 88 degrees with subnatural width. It is demonstrated that Doppler broadening has a destructive effect on the MOR of the polarization direction of the probe field. The results of our study can be used for selecting narrow band of wavelengths and polarization converter for efficient switching of TM/TE polarization modes in optical communication, the depolarization backscattering lidar, polarization spectroscopy and precision measurements.

Doppler shift spectroscopy of powerful neutral beams

Abstract: An optical diagnostic is reported which measures the parameters of an intense hydrogen or deuterium neutral beam by observation of the Doppler shifted Balmer alpha or beta lines emitted by fast atoms in the beam at several locations in the neutralizer. The spectrum of blue shifted and red shifted light emitted along optic axes which lie in planes perpendicular and parallel to the grid rails of the ion source is recorded by an optical multichannel analyzer which is interfaced to a computer. The light is Doppler shifted sufficiently to resolve the three energy components of the beam resulting from the H+, H+2, and H+3 ions accelerated by the ion source. From the Doppler broadening of each peak the beam divergence parallel and perpendicular to the accelerator slots can be measured. A model is presented whereby the energy distribution can be determined from the intensity of each peak. The spectroscopic results for energy distribution are in agreement to within 5% with momentum analysis by a magnetic mass spec...