Deuterium, abundance

Fig. 2. The deuterium abundance (by number relative to hydrogen), yi> = 105(D/H), derived from high redshift, low metallicity QSOALS [3] (filled circles). The metallicity is on a log scale relative to solar depending on the line-of-sight, X may be oxygen or silicon. Also shown is the solar system abundance (filled triangle) and that from observations of the local ISM (filled square).

Fig. 2. Stochastic accretion models for an open system. The infalling gas is assumed to be extragalactic material with standard Big Bang nucleosynthetic abundances (Xo = 0.758, Yo = 0.242, 2D=6.5xlCP5, SBBN) and zero metals, (a) Star formation rate vs. time for the thin disk. From the top to the bottom the curves refer to 44%, 10%, 5%, 1% and no mass added, (b) Metallicity vs. time for the thin disk. From the top to the bottom the curves refer to standard case (no mass added), 1%, 5%, 10%, 44% of mass added. The metallicity evolution curve illustrates the relatively weak dilution effects that are offset by continuing star formation. Details for the Deuterium abundances are shown in Fig. 3...

The deuterium abundance, on the other hand, is a steeply decreasing function because it is destroyed by two-body reactions with p, n, D and 3He. 3He declines more gently because this nucleus is more robust. 7Li has a bimodal behaviour because at low baryon densities it is synthesized from 3H by reaction (Eq. 4.46) and both nuclei are destroyed by two-body reactions, whereas at higher densities it... 

The two error terms refer to Yp and the regression slope respectively. In contrast to some earlier work, based on less homogeneous data sets and apparently affected by underlying absorption lines, notably in I Zw 18, this result, together with a similar one by Peimbert, Luridiana and Peimbert (2007), gives a primordial helium abundance in excellent agreement with the one predicted theoretically on the basis of the microwave background fluctuations and the lower estimates of deuterium abundance (see Fig. 4.3), a comparatively small value of about 2 for AT/AZ and no... 

Show that, in the Simple model (no inflow and no Galactic wind), the evolution of deuterium abundance in the interstellar medium is given by... 

Show that, in Larson s extreme inflow model (see Section 8.5.1), assuming infalling material to be pristine with primordial abundances, the deuterium abundance evolves according to... 

Estimates of primordial helium and deuterium abundance with Big Bang nucleosynthesis theory limit number of light neutrino families to 4 or less (Schramm et al). 

The NMR determinations of the site-specific hydrogen isotope ratios at natural deuterium abundance permitted one to assess primary and secondary thermodynamic fractionation factors in exchange reactions avoiding the synthesis of selectively labelled reagents and their degradations691. 

Then, in the 1990 s, the accurate determination of the primeval deuterium abundance changes the strategy. Schramm and his collaborators introduced the deuteronomy (see Schramm Turner, 1997). Also, because the Big Bang deuterium production decreases rapidly with baryon density and its post Big Bang history (or chemical evolution) is simple - stars only destroy D - primordial deuterium became the best baryometer. It pegged the baryon density and led to accurate predictions for the other fight elements. 

From the isotopic decomposition of normal H one finds that the mass-2 isotope, 2H, or D (for deuterium) as it is also written, is relatively rare. On Earth it constitutes only 0.015% °f all H isotopes. This makes it 6670 times less abundant than 1H. This information comes from the isotopic analysis of sea water however, deuterium is even more rare in the universe Modern observations of the interstellar gas reveal it to be ten times less abundant relative to H than it is in sea water. This makes the deuterium abundance of Earth the first great isotopic anomaly namely, that D in sea water has been enriched tenfold by the historical processes by which the Earth s oceans were formed from the initial interstellar matter from which the solar system was built. 

The last parameter of big bang nucleosynthesis. .. is being pinned down by measurements of the deuterium abundance in high-redshift hydrogen clouds. 

Schramm wanted to find out if the abundances of the light elements were consistent with big bang cosmology. To answer this question, he would need to refine theoretical predictions based on the tenets of big bang cosmology, design and carry out astronomical experiments to measure the abundances of the four light elements, and compare the results. As we shall see, the results for deuterium are particularly important—deuterium abundance depends on one and only one important parameter the density of matter. 

A. Songalla, L. L. Cowle, C. J. Hogan, and M. Rugers, Deuterium Abundance and Background Radiation Temperature in High-Redshift Primordial Clouds, Nature 368, 599-604 (1994). 

Figure 3 Map of the deuterium abundance in solar system objects, plotted as D/H mole fraction. The carrier molecules for which deuterium has been measured in each object are labeled. The protosolar value, derived from measurements of He products of deuterium fusion in the Sun, and deuterium in the local region of the galaxy, is given, as are values for a carbonaceous chondrite meteorite, the Earth s oceans, and comets (source...

Since the 4 He mass fraction is relatively insensitive to the baryon density, it provides an excellent probe of any changes in the expansion rate. The faster the universe expands, the less time for neutrons to convert to protons, the more 4He will be synthesized. The increase in Y for modest changes in S is roughly AY 0.16(A — f) 0.013A/V,. In Fig. 2 are shown the BBN-predicted Y versus the BBN-predicted Deuterium abundance (relative to Hydrogen) for three choices of N (N = 3 + AN ). 

Figure 2. The BBN-predicted primordial 4He mass fraction Y as a function of the BBN-predicted primordial Deuterium abundance (by number relative to Hydrogen) for three choices of N . The width of the bands represents the theoretical uncertainty, largely due to that of the neutron lifetime rn.

Figure 3. The deuterium abundance, D/H, versus redshift, z, from observations of QSOALS (filled circles). Also shown for comparison are the D-abundances for the local ISM (filled square) and the solar system ( Sun filled triangle).

As discussed earlier, the stellar and Galactic chemical evolution uncertainties afflicting 3He are so large as to render the use of 3He to probe or test BBN problematic therefore, I will ignore 3He in the subsequent discussion. There are a variety of equally valid approaches to using D, 4He, and 7Li to test and constrain the standard models of cosmology and particle physics (SBBN). In the approach adopted here deuterium will be used to constrain the baryon density (r] or, equivalently, if>h 2 ) Within SBBN, this leads to predictions of Yp and [Li]p. Indeed, once the primordial deuterium abundance is chosen, r/ may be eliminated and both Yp and [Li] p predicted directly, thereby testing the consistency of SBBN. 

Figure 9. The diagonal band is the SBBN-predicted deuterium abundance (by number relative to hydrogen) as a function of the nucleon-to-photon ratio r/w (the width of the band accounts for the theoretical uncertainties in the SBBN prediction). The horizontal band is the 1<7 range in the adopted primordial deuterium abundance. The vertical band is, approximately, the corresponding SBBN-predicted y range.

Perhaps the most dramatic consequence of removing CO from the gas phase by freezing of the dust grains in very cold prestellar regions is the observation of extremely enhanced deuterium abundances in molecules. CO destroys H+ by... 

Songaila, A., Cowie, L.L., Hogan, C.J., andRugers, M., 1994. Deuterium abundance and background radiation temperatures in high redshift primordial clouds. Nature, 368, 599-604. 

How many kilograms of water must be processed to obtain 2.0 L of D2 at 25°C and 0.90 atm pressure Assume that deuterium abundance is 0.015 percent and that recovery is 80 percent. 

To simplify the treatment further, only low deuterium abundances are considered, so that the atom fractions of deuterium in liquid x and in vapor y in the streams leaving stage i are related by... 

An expression will be derived for the dependence of a on the physical properties of the water-hydrogen sulfide system, temperature and pressure. The slight dependence of a on deuterium content will be neglected by considering only low deuterium abundances, at which D,0 In this limiting case, the expression for a reduces to... 

Equation (13.144) is the exact expression for the deuterium exchange separation factor in liquid-vapor mixtures of water and hydrogen sulfide at low deuterium abundances. Values evaluated from it are customarily used without correction up to 15 percent deuterium. When the vaporization of water into H2S is smaU (H<1) and the solubility of HjS in water is small... 

The protosolar D/H ratio. The protosolar deuterium abundance is an upper limit to the primordial abundance of this isotope and provides a crucial observational test for the Big Bang cosmological model (Schramm 1993). For example, the primordial deuterium... 

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