The 12C/13C and 160/180 ratios in the solar photosphere

The abundances of 12C, 13C and 18O in the solar photosphere have been measured from more than 900 lines of the fundamental vibration-rotation bands of isotopically substituted CO species. It is found that log N(12C) = 8.71 +- 0.10, 12C/13C = 84 +- 5, and 16O/18O = 440 +- 50, i.e. the solar and terrestrial isotopic ratios are essentially identical. These results, together with the known abundances of lighter isotopes, constrain unorthodox models of the Sun's evolution which require the surface layers to have been subjected to high temperatures. A requirement that the derived molecular abundance be independent of the excitation potential and wavelength is not met by all empirical model solar atmospheres. (author)