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Electronic Sputtering Analysis of Astrophysical Ices |
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| Authors: | L S Farenzena P Iza R Martinez F A Fernandez-Lima E Seperuelo Duarte G S Faraudo C R Ponciano M G P Homem A Naves de Brito K Wien E F da Silveira |
| Institution: | 1. Departamento de Física, Pontifícia Universidade Católica, 22543-970, Rio de Janeiro, Brazil 2. Centro Federal de Educa??o Tecnológica de Química de Nilópolis, 26530-060, Nilópolis, RJ, Brazil 3. Laboratório Nacional de Luz Síncrotron, Box 6192, 13084-971, Campinas, SP, Brazil 4. Guest of the Institute of Nuclear Physics, Technical University, 64289, Darmstadt, Germany |
| Abstract: | Experimental results on fast ion collision with icy surfaces having astrophysical interest are presented. 252Cf fission fragments projectiles were used to induce ejection of ionized material from H2O, CO2, CO, NH3, N2, O2 and Ar ices; the secondary ions were identified by time-of-flight mass spectrometry. It is observed that all the bombarded frozen gas targets emit cluster ions which have the structure XnR±, where X is the neutral ice molecule and R± is either an atomic or a molecular ion. The shape of the positive or negative ion mass spectra is characterized by a decreasing yield as the emitted ion mass increases and is generally described by the sum of two exponential functions. The positive ion water ice spectrum is dominated by the series (H2O)nH3O+ and the negative ion spectrum by the series (H2O)nOH− and (H2O)nO−. The positive ion CO2 ice spectrum is characterized by R+ = C+, O+, CO+, O2+ or CO2+ and the negative one by R− = CO3−. The dominant series for ammonia ice correspond to R+ = NH4+ and to R− = NH2−. The oxygen series are better described by (O3)nOm+ secondary ions where m = 1, 2 or 3. Two positive ion series exist for N2 ice: (N2)nN2+ and (N2)nN+. For argon positive secondary ions, only the (Ar)nAr+ series was observed. Most of the detected molecular ions were formed by one-step reactions. Ice temperature was varied from ∼20 K to complete sublimation. |
| Keywords: | Cometary ice condensed gas (H2O CO2 CO NH3 N2 O2 Ar) ion cluster TOF SIMS temperature dependence |
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