43 research outputs found
The absorption spectrum of short-lived isotopic variant of water, HâÂčâ”O: Tentative detection at the Earth's atmosphere
A calculated infrared vibrationârotation spectrum of isotopically modified water, H215O, is presented. Oxygen-15 has a half-life of about 2 minutes and H215O may be formed in the atmosphere during thunderstorms as a result of photonuclear processes or when the atmosphere is irradiated by cosmic Îł-rays. Variational nuclear motion calculations of vibrational and vibrational-rotational levels up to 25000 cmâ1 and up to J = 10 in angular momentum are performed within the framework of the Born-Oppenheimer approximation using an accurate water potential function. The line shape parameters for H215O are estimated. Spectral ranges that are promising for the detection of H215O in the atmosphere are identified and a search for spectral signatures conducted. A spectral feature is tentatively assigned to the 752 (0 1 0) - 643 (0 0 0) line of H215O
Interstellar Turbulence II: Implications and Effects
Interstellar turbulence has implications for the dispersal and mixing of the
elements, cloud chemistry, cosmic ray scattering, and radio wave propagation
through the ionized medium. This review discusses the observations and theory
of these effects. Metallicity fluctuations are summarized, and the theory of
turbulent transport of passive tracers is reviewed. Modeling methods, turbulent
concentration of dust grains, and the turbulent washout of radial abundance
gradients are discussed. Interstellar chemistry is affected by turbulent
transport of various species between environments with different physical
properties and by turbulent heating in shocks, vortical dissipation regions,
and local regions of enhanced ambipolar diffusion. Cosmic rays are scattered
and accelerated in turbulent magnetic waves and shocks, and they generate
turbulence on the scale of their gyroradii. Radio wave scintillation is an
important diagnostic for small scale turbulence in the ionized medium, giving
information about the power spectrum and amplitude of fluctuations. The theory
of diffraction and refraction is reviewed, as are the main observations and
scintillation regions.Comment: 46 pages, 2 figures, submitted to Annual Reviews of Astronomy and
Astrophysic
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.