Ion cluster desorption from frozen NH3 induced by impact of fast multi-charged ions

Abstract:

Ion cluster desorption yields due to the impact of 252Cf fission fragments on condensed ammonia are determined. Identification and abundance of the ion desorbed species were provided by a time-of-flight mass spectrometer. Ammonia ice thin layers deposited on Au film were heated from 25K to complete sublimation. The typical pressure during heating process was 10−8mbar. Measurements in the 25–150K temperature range show emission of (NH3)nNHm± ion clusters, where n varies from 0 to ∼30 and m varies from 0 to 3 (for negative ions) or to 5 (for positive ions). The distribution is described by the sum of two decaying exponentials when n increases, which is interpreted by the simultaneous occurrence of two cluster formation regimes: (i) recondensation of sublimated molecules from the projectile track and (ii) emission of pre-formed bulk fragments from the periphery of the impact site. Moreover, the cluster …

Año de publicación:

2006

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Fuente:

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