Carbon Monoxide in the Sun.

Nearly 300 llnes of carbon monoxide have been identified in the spectrum of the solar limb between 2.29 and 2.50 . The lines belong to the overtone bands 24), 31, 42, 33, , and 7-5. Analysis of the solar wave lengths has led to a new determination of the vibrational and rotational constants of the CO molecule. The measured absorption coefficients of Penner and Weber and the theoretical values of Scholz have been applied to the measured equivalent widths at the center of the disk. The resulting equivalent abundance of CO is 1.45 X t0' molecules per square centimeter above the photosphere, and the excitation temperature is 4300 K. It is shown from model-atmosphere calculations that solar Co is concentrated near the top of the photosphere and hence that the derived excitation temperature is consistent since it agrees with the boundary temperature. At present, it is not known whether the dissociation energy of CO is 9.6 or 11.1 e.v. If the lower value is correct, the solar-line intensities suggest that the boundary temperature is less than 4500 K. The exact value of the temperature depends on the choice of atomic abundances for 0 and C. The low intensities of the fundamental band lines of CO in the 4.6 region are explained as a consequence of (1) the high opacity of the solar atmosphere at long wave lengths, (2) the importance of stimulated emissions in the infrared, and (3) the small collisional line widths in the sun's outer layers.