Unusual stability of polycyclic aromatic hydrocarbon radical cations in amorphous water ices up to 120 K: Astronomical implications
Unusual stability of polycyclic aromatic hydrocarbon radical cations in amorphous water ices up to 120 K: Astronomical implications
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DOI：
10.1086/498816
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发表时间：
2006-02-10
影响因子：
4.9
通讯作者：
Allamandola, LJ
中科院分区：
文献类型：
--
作者：
Gudipati, MS;Allamandola, LJ
发现PAH自由基阳离子quaterrylene（+）（QTR（+），C40H20）在无定形水冰中直到120 K是稳定的。一个仔细的，30天，从20到190 K的含有QTR（+）的水冰的缓慢升温显示，QTR（+）不显示任何反应性的迹象，直到120 K，在该温度下，无定形到结晶水冰的相变开始。在较高的温度下，由于QTR自由基阳离子的吸收迅速减少，但持续到水冰本身在170 K左右升华。由于没有证据表明中性QTR在升温或与冰中其他被捕获的反应中间体反应时会恢复，我们推断QTR（+）在120 K以上的升温过程中与水冰本身反应。早些时候，我们发现，PAH电离是定量的水冰和PAH电离能降低高达2 eV。这些不寻常的发现宇宙冰化学和物理的一些影响进行了简要讨论。
The PAH radical cation quaterrylene(+) (QTR(+), C40H20) is found to be stable in amorphous water ice up to 120 K. A careful, 30 day, slow warm-up of water ice containing QTR(+) from 20 to 190 K revealed that QTR(+) does not show any sign of reactivity up to 120 K, the temperature at which the phase transition of amorphous to crystalline water ice begins. At higher temperatures the absorption due to the QTR radical cation diminishes rapidly but persists until the water ice itself sublimes around 170 K. From the absence of evidence for the recovery of neutral QTR upon warm-up or reactions with other trapped reaction intermediates in the ice, we infer that QTR(+) reacts with the water ice itself during warm-up above 120 K. Earlier we found that PAH ionization is quantitative in water ice and PAH ionization energy is lowered by up to 2 eV. Some implications of these unusual findings for cosmic ice chemistry and physics are briefly discussed.