Absolute isotopic abundance ratios and the atomic weight of a reference sample of silicon

Abstract

Ab solute va lu es have been obtained for th e isotopic a bund a nce rati os of a re fe re nce sa mpl e of s ilico n us ing e lec tron impa ct mass s pectrom etry. Sa mpl es of known isoto pi c co mpos it ion pre pared fro m nearly isotop ica lly pure se pa rated sili co n isotopes we re used to ca librate th e ma ss s pectrom e te rs. The res ult ing absolute ,sS i/,JOS i ratio = 29.74320 ± 0.00747 and th e 29S i/,,°S i ratio = 1. 50598 ± 0.00086 whi c h yield at om pe rcen ts of '"S i = 92.229:n . 0.00155. " 'Si =,1.()6982 I 0.00124 and :lIISi = :). 10085 I 0.00074. The atomic weight ca lc ulated from thi s isotopic co mpos ition is 28.085526 · 0.000056. Th e indi cated un ce rtainti es are overall limit s of e rror based o n 95 perce nt confidence limit s for th e mea ns a nd a ll owan ces for th e effec ts of kn ow n sources of poss ibl e s yste ma tic e rror. A study of natura l '"S i/,IIIS i rati o variations re ported in th e literature e xtend s tb e es timat ed un ce rt a int y in th e atomic we ight of natural s ili co n to ' 0.000.39.Key word s: Absolut e ratios; a tomi c we ight: iso topi c abundan ce: s ili co n .• Prese nt aJdrt:ss: Tel edyne Isutopcs. Ti monium. Maryland 2 1200.

Atomic weights of the elements 2009 (IUPAC Technical Report)

“…The lower bound of the atomic-weight interval corresponds to silicon from precipitated siliceous cement in sandstone [48], and the upper bound corresponds to silicon in rice grains [49]. The previous standard atomic-weight value A r (Si) = 28.0855(3), recommended in 1975 [51], was based on superior mass-spectrometric measurements [52]. In the …”

The 1986 adjustment of the fundamental physical constants

“…The NBS value is based on determinations of the isotopic composition (Barnes et al , 1975;Ku, 1983) and density of pure Si single crystals (Bowman, Schoonover, and Carroll, 1974a, 1974b, corrected for known impurities and expressed in terms of the density at 22. 5'C in vacuum.…”

The Potential use of Silicon Isotope Composition of Biogenic Silica as a Proxy for Environmental Change

“…The relative abundances on Earth of the stable isotopes are 92.23% ( 28 Si), 4.67% ( 29 Si), and 3.10% ( 30 Si) [1]. The silicon isotope ratios ( 30 Si/ 28 Si and 29 Si/ 28 Si) of materials are expressed on the delta-scale (δ) in terms of per mille (‰):…”