Mathematics – Logic
Scientific paper
May 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...202.2913b&link_type=abstract
American Astronomical Society Meeting 202, #29.13; Bulletin of the American Astronomical Society, Vol. 35, p.739
Mathematics
Logic
Scientific paper
Precision measurement of the primordial abundance of the light elements is one of the fundamental tests of the Big Bang. The primordial abundance of helium, Y p, the ratio of He to H by mass, is measured from emission lines that form during the recombination-decay process, He+ + e- -> He0(nL) + hν followed by radiative cascade. A definitive test of the Big Bang requires an accuracy of 1% or better. Y p is measured from ratios of intensities of He I and H I recombination lines in H II regions. The density ratio n(He+)/n( H+) is proportional to the observed line intensities. All previous studies of He I recombination coefficients have assumed that the triplets and singlets are distinct radiative cascade systems that communicate only through electron exchange collisions. Actually, certain large-angular-momentum levels have strongly mixed spin multiplicities, leading to conventional electric-dipole decays that act to mix the singlets and triplets. We present calculations of He I recombination coefficients at a temperature 10,000 K in "Case B" explicitly including fine structure in the helium transition rates and energies. Changes 1% or greater are observed in several important emission line intensities, and these changes may effect the deduced Y p by cosmologically significant amounts. This project is supported by the NSF and NASA through grants AST 0071180 and NAG5-8212.
Bauman Robert P.
Ferland Gary J.
MacAdam K. B.
No associations
LandOfFree
He/H ratio for Cosmology: Accurate He recombination coefficients including fine structure and singlet-triplet mixing does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with He/H ratio for Cosmology: Accurate He recombination coefficients including fine structure and singlet-triplet mixing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and He/H ratio for Cosmology: Accurate He recombination coefficients including fine structure and singlet-triplet mixing will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1367806