Reaction rates of proton and deuteron induced reactions on lithium

Abstract

Abstract:Reaction rates are calculated for recently available low-energy data on 7Li(p,a)4He, 6Li(p,3He)4He and SLi(d,a)4He and compared to literature values. While the new rates are considered to be more accurate, their absolute magnitude agrees within about 10% with the most recent compilation. PACS: 25.00For astrophysical purposes the knowledge of low energy thermonuclear reaction rates NA (av) is essential.The bracketed quantity is the usual energy averaged product of cross section times the relative velocity of the interacting particles, and NA is Avogadro's con-of the reactions 7Li(p,a)4He, 6Li(p,aHe)4He and 6Li(d,~)4He to very low energies (13 keV, 11 keV and 16 keV centerof-mass energy, respectively) were performed in order to study the effect of electron screening. With the fitting procedure described in [2-4] the effect of screening (which causes a steep increase of the low-energy data) can be extracted, so that the resulting astrophysical Sfactor [1] is that of bare nuclei.

Lithium Depletion in Fully Convective Pre–Main‐Sequence Stars

“…Over the range of temperatures (T 6 ≡ (T /10 6 K) < 6) appropriate for this work, the reaction rate is N A σv = Sf scr T −2/3 6 exp(−aT −1/3 6 ) cm 3 s −1 g −1 where S = 6.4 × 10 10 and a = 84.72 (Caughlan & Fowler 1988) and f scr is the screening correction factor (Salpeter & Van Horn 1969). Raimann (1993) recently discussed new experimental results at low energies (≈ 11-13 keV) and updated S to 7.2 × 10 10 .…”

“…) cm 3 s −1 g −1 where S = 6.4 × 10 10 and a = 84.72 (Caughlan & Fowler 1988) and f scr is the screening correction factor (Salpeter & Van Horn 1969). Raimann (1993) recently discussed new experimental results at low energies (≈ 11-13 keV) and updated S to 7.2 × 10 10 .…”

“…Although solving the depletion equation ( 10) numerically is straightforward, an analytic fitting formula for the time (and therefore the radius and luminosity from equations [3] and [4]) as a function of depletion is also helpful. The age at a given depletion (we use Raimann's [1993] rates; using Caughlan's and Fowler's [1988] rates changes t depl by no more than a few percent) for 2000 K < T eff < 4000 K, 0.075M ⊙ < M < 0.5M ⊙ , and 0.65 < X < 0.75 is…”

Implications of a Subthreshold Resonance for Stellar Beryllium Depletion

“…The 9 Be(p, α) 6 Li Cross-Section An important part of the microphysics in any stellar model is the destruction rates of the light elements. The lithium rates have recently been adjusted (Raimann 1993) slightly. For the case of beryllium, there is a potentially strong correction to the CF88 rates.…”

Lithium abundance is a gravitational model dependent quantity

“…where T c6 ≡ T c /10 6 K and f scr is the screening correction factor while S and a are dimensionless parameters in the fit to the reaction rate. For our range of temperatures, the proton-capture rate parameters for the reaction 7 Li(p, α) 4 He are S = 7.2 × 10 10 and a = 84.72 [27,31,32]. Since we are dealing with polytropic stars with the polytropic index n = 3/2, the temperature is T = T c θ(ξ) while density is expressed as ρ = ρ c θ 3/2 (ξ).…”