Doppler broadening

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

Stark Broadening of the B III 2s-2p Lines

Abstract: We present a quantum-mechanical calculation of Stark linewidths from electron-ion collisions for the ${2s}_{1/2}{\ensuremath{-}2p}_{1/2,3/2},$ $\ensuremath{\lambda}=2066$ and 2067 \AA{}, resonance transitions in B III. The results confirm previous quantum-mechanical $R$-matrix calculations, but contradict recent measurements and semiclassical and some semiempirical calculations. The differences between the calculations can be attributed to the dominance of small $L$ partial waves in the electron-atom scattering, while the large Stark widths inferred from the measurements would be substantially reduced if allowance is made for hydrodynamic turbulence from high-Reynolds-number flows and the associated Doppler broadening.

Vibrational Perturbations and Ligand–Layer Coupling in a Single Crystal of Au144(SC2H4Ph)60 Nanocluster

Abstract: We have determined vibrational signatures and optical gap of the Au144(PET)60 (PET: phenylethylthiol, SC2H4Ph) nanocluster solvated in deuterated dichloromethane (DCM-D2, CD2Cl2) and in a single crystal. For crystals, solid-state (13)C NMR and X-ray diffraction were also measured. A revised value of 2200 cm(-1) (0.27 eV) was obtained for the optical gap in both phases. The vibrational spectra of solvated AU144(PET)60 closely resembles that of neat PET, while the crystalline-state spectrum exhibits significant inhomogeneous spectral broadening, frequency shifts, intensity transfer between vibrational modes, and an increase in the overtone and combination transition intensities. Spectral broadening was also observed in the (13)C NMR spectrum. Changes in the intensity are explained due to vibrational coupling of the normal modes induced by the crystal packing, and the vibrational broadening is caused by ligand-environment inhomogeneity in the crystal. This indicates a pseudocrystalline state where the cluster cores are arranged in periodic fashion, while the ligand-layer molecules between the cores form amorphous structures.

The mass and energy budget of Cassiopeia A

Abstract: Further analysis of X-ray spectroscopy results recently obtained from the MOS CCD cameras on-board XMM-Newton provides a detailed description of the hot and cool X-ray emitting plasma in Cas A. Measurement of the Doppler broadening of the X-ray lines is consistent with the expected ion velocities, ~1500 km/s along the line of sight, in the post shock plasma. Assuming a constant total pressure throughout the remnant we estimate the total remnant mass as 10 Msun and the total thermal energy as 7E43 J. We derive the differential mass distribution as a function of ionisation age for both X-ray emitting components. This distribution is consistent with a hot component dominated by swept up mass heated by the primary shock and a cool component which are ablated clumpy ejecta material which were and are still being heated by interaction with the preheated swept up material. We calculate a balanced mass and energy budget for the supernova explosion giving 1E44 J in ejected mass; approximately 0.4 Msun of the ejecta were diffuse with an initial rms velocity of 15000 km/s while the remaining ~1.8 Msun were clumpy with an initial rms velocity of ~2400 km/s. Using the Doppler velocity measurements of the X-ray spectral lines we can project the mass into spherical coordinates about the remnant. This provides quantitative evidence for mass and energy beaming in the supernova explosion. The mass and energy occupy less than 4.5 sr (<40 % of the available solid angle) around the remnant and 64 % of the mass occurs in two jets within 45 degrees of a jet axis. We calculate a swept up mass of 7.9 Msun in the emitting plasma and estimate that the total mass lost from the progenitor prior to the explosion could be as high as ~20 Msun.