Lithium and the Internal Circulation of the Sun.

The profiles and intensity of the Li resonance doublet at X 6708 have been measured on the solar disk and in the spot penumbra, with dispersion 0.7 A/mm. A special technique was required, since the lines have a central absorption less than 3 per cent. The isotope ratio Li6/Li7 is less than 0.25 and may be the same as on the earth, 0.08. From the equivalent width the abundance of Li I has been found to be 6.7 x 10' atom/gm. Two different methods of analysis yield the abundance ratio H/Li as 1.4 X 10" or 0.6 X 10". The ratio Li/Ca is 7 X 10-6. Compared to the other metals, Li is only one one-hundredth as abundant as on earth. Analysis of the nuclear cross-sections for proton capture shows that in equilibrium with protons the ratio Li6/Li3 should be small, in agreement with observation. The lifetime of Li is short at T > 3 X 106 degrees. The deficiency of Li in the sun may arise from a very slow circulation down to at least half the solar radius with period near 7 X 10' years. If the circulation is more rapid, all Li should have been destroyed. Accretion from interstellar matter can maintain the observed Li abundance only if the space density is improbably high.