從宇宙間物質表面濺射出原子、分子或離子的作用是造
成一些太空環境中表面物質的質量轉換和演化的一個重要
過程，包括彗星、小行星、行星的衛星表面、土星環、或星
際間物質的塵埃上的中性原子、分子及離子的脫附率讓我們
了解冰晶表面受太陽紫外光作用形成的侵蝕率。
本實驗是以氫氣微波放電管產生的真空紫外光為光
源，產生的光以121.6 nm 波長的光為主，照射鍍在石英基板
上的冰晶。收集光脫附作用（photodesorption）產生的離子，
去計算出總離子脫附率（total ion yield）。作為瞭解光脫附造
成冰晶的質量演化（mass evolution）的一個重要依據。
在77K 溫度下，測得三種不同的冰晶的總離子脫附率分
別為純水 0.00065 個/光子，純水加二氧化碳為 0.00058 個/
光子，以及純水加氨為 0.00044 個/光子。這實驗的結果和吳中
榮教授（C. Y. Robert Wu）以58.4 nm 光照射純水冰晶的結
果一致。

Sputtering of neutral and ionic atoms and molecules from surfaces
of astronomical materials is an important process from mass transfer,
mass evolution, and chemical evolution points of view. In a number of
astronomical environments, e.g., comets, asteroids, planetary satellites
and rings, and interplanetary dust grains, the yield, including ion and
neutral desorption, will allow us to determine the erosion rate due to
electronic excitation processes, which may be very important in cases
where solar VUV-EUV photons can reach the surfaces of icy bodies.
This experiment collected sputtered ions from ices which were
illuminated by VUV from a microwave-stimulated hydrogen flow
discharge lamp with main emission at Lyman-α at 121.6 nm. The
measured ion current will be one of the vital factors in understanding
mass evolution of ices on the interstellar matters.
The total ion yields of H2O、H2O+CO2、H2O+NH3 three different
ices prepared at 77 K were found to be 0.00065 ions/photon in H2O ice,
0.00058 ions/photon in H2O+CO2 ice, 0.00044 ions/photon in H2O+ NH3
ice. The results agrees quite well with the experimental data measured by
C. Y. Robert Wu although the later work was reported using a 58.4 nm
lamp instead of 121.6 nm in this case.

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