Westley M S, Baragiola R A, Johnson R E, Baratta G A
University of Virginia, Charlottesville 22901.
Nature. 1995 Feb 2;373(6513):405-7. doi: 10.1038/373405a0.
Dust grains in the interstellar medium and the outer Solar System commonly have a coating of water ice, which affects their optical properties and surface chemistry. The thickness of these icy mantles may be determined in part by the extent of photodesorption (photosputtering) by background ultraviolet radiation. But this process is poorly understood, with theoretical estimates of the photodesorption rate spanning several orders of magnitude. Here we report measurements of the absolute ultraviolet photodesorption yield of low-temperature water ice. Our results indicate that the rate of photodesorption is appreciable. In particular, it can account for the absence of icy mantles on grains in diffuse interstellar clouds, it exceeds solar-wind ion erosion and sublimation in the outer Solar System, and it is important in determining the lifetimes of icy mantles in dense molecular clouds.
星际介质和太阳系外层的尘埃颗粒通常覆盖着一层水冰，这会影响它们的光学特性光学冰壳的厚度可能部分取决于背景紫外辐射的光解吸（光溅射）程度。但这个过程目前还了解得很少，光解吸速率的理论估计值相差几个数量级。在这里，我们报告了低温水冰绝对紫外光解吸产率的测量结果。我们的结果表明，光解吸速率相当可观。特别是，它可以解释弥漫星际云中尘埃颗粒上没有冰壳的现象，它超过了太阳系外层太阳风离子侵蚀和升华的速率，并且在确定致密分子云中冰壳的寿命方面很重要。
