Science. 1993 Jul 9;261(5118):184-6. doi: 10.1126/science.261.5118.184.
Atomic sodium is a useful tracer of the tenuous lunar atmosphere because of its high efficiency in scattering sunlight at the D(1) (5896 angstroms) and D(2) (5890 angstroms) wavelengths. In 1988, Earth-based instruments revealed the presence of sodium at a density of less than 50 atoms per cubic centimeter at lunar altitudes below 100 kilometers. Telescopic observations that are made with a coronograph technique to block out the disk of the moon allow a true picture of the circumiunar atmosphere to be obtained and show the presence of sodium out to a distance of several lunar radii. The distribution of sodium has a solar zenith angle dependence, suggesting that most of the sodium that reaches great altitudes is liberated from the moon's surface by solar photons (by heating or sputtering) or by solar wind impact, in contrast to a source driven by uniform micrometeor bombardment.
原子钠是一种有用的月球稀薄大气示踪剂，因为它在散射太阳光 D(1)（5896 埃）和 D(2)（5890 埃）波长方面非常有效。1988 年，地基仪器显示，在 100 公里以下的月球高度上，钠的密度小于每立方厘米 50 个原子。使用日冕仪技术进行的望远镜观测可以阻挡月球的盘面，从而获得真正的月球周围大气图像，并显示出钠存在于几个月球半径的距离之外。钠的分布具有太阳天顶角依赖性，这表明到达高海拔的大部分钠是由太阳光子（通过加热或溅射）或太阳风撞击从月球表面释放出来的，而不是由均匀的微流星体撞击驱动的。
