Doppler broadening

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

Line strengths and transition dipole moment of the ν2 fundamental band of the methyl radical

Abstract: The line strengths of nine Q-branch lines in the ν2 fundamental band of the methyl radical in its ground electronic state have been measured by diode laser absorption spectroscopy. The vibration–rotation spectrum of methyl was recorded in a microwave discharge in ditertiary butyl peroxide heavily diluted in argon. The absolute concentration of the radical was determined by measuring its kinetic decay when the discharge was extinguished. The translational, rotational, and vibrational temperatures, also required to relate the line strengths to the transition dipole moment, were determined from relative integrated line intensities and from the Doppler widths of the lines after allowing for instrumental factors. The line strengths of the nine Q-branch lines were used to derive a more accurate value of the transition dipole moment of this band, μ2=0.215(25) D. Improved accuracy over earlier measurements of μ2 (derived from line strengths of single lines) was obtained by integrating over the complete line profi...

Spectral broadening of picosecond laser pulses in optical fibres

Abstract: Picosecond light pulses of a passively mode-locked ruby laser (pulse duration Δt L≈35 ps) are spectrally broadened in optical fibres of core diameters from 4 μm to 600 μm. Combining the effects of self-phase modulation, stimulated Raman scattering, and parametric four-photon interaction in an 8-μm core fibre of 4 m length with the effect of selective spectral attenuation in a ruby rod resulted in rather smooth spectra extending from 685 nm to 830 nm (spectral width ≈2300 cm-1).

Linking the thermodynamic temperature to an optical frequency: recent advances in Doppler broadening thermometry.

Abstract: Laser spectroscopy in the linear regime of radiation-matter interaction is a powerful tool for measuring thermodynamic quantities in a gas at thermodynamic equilibrium. In particular, the Doppler effect can be considered a gift of nature, linking the thermal energy to an optical frequency, namely the line centre frequency of an atomic or molecular spectral line. This is the basis of a relatively new method of primary gas thermometry, known as Doppler broadening thermometry (DBT). This paper reports on the efforts that have been carried out, in the last decade, worldwide, to the end of making DBT competitive with more consolidated and accurate methodologies, such as acoustic gas thermometry and dielectric constant gas thermometry. The main requirements for low-uncertainty DBT, of both theoretical and technical nature, will be discussed, with a special focus on those related to the line shape model and to the frequency scale. A deep comparison among the different molecules that have been selected in successful DBT implementations is also reported. Finally, for the first time, to the best of my knowledge, the influence of refractive index effects is discussed.

Broad-band high-repetition-rate source for spectrally sliced WDM

Abstract: A uniform 35-nm-wide spectrum is generated by broadening the output from a 2.5-GHz mode-locked femtosecond fiber laser in dispersion shifted fiber. The obtained spectrum is suitable for spectral slicing and wavelength-division-multiplexed applications. The spectral broadening in dispersion shifted fiber is optimized as a function of the launched pulse chirp parameter.

Two-detector Doppler broadening study of enhancement in Al

Abstract: Enhancement due to positron-electron correlation has been studied in Al by calculating and measuring Doppler profiles and positron lifetimes. It is found that only the local density enhancement of Puska, Seitsonen and Nieminen can simultaneously reproduce the profile and the lifetime, but our analysis suggests that a GGA-type enhancement of reduced strength would likely give even better results.