Chemical quenching and inhibition of positronium in Cr2O3/Al2O3 catalysts
Chemical quenching and inhibition of positronium in Cr2O3/Al2O3 catalysts
复制标题
DOI：
10.1007/s11859-011-0755-6
复制
发表时间：
2011-08
影响因子：
--
通讯作者：
Shu-lan Huang;Y. Dai;Hongjun Zhang;Zhiquan Chen
中科院分区：
文献类型：
--
作者：
Shu-lan Huang;Y. Dai;Hongjun Zhang;Zhiquan Chen
用正电子寿命和符合多普勒展宽（CDB）技术研究了Cr_2O_3/Al_2O_3催化剂的孔结构和孔的表面化学性质。从正电子寿命谱中可以分辨出四个寿命分量，其中两个长寿命分量和两个短寿命分量。两个长寿命τ 4和τ 3分别归因于大孔和微孔中的正电子偶素（o-Ps）湮灭。随着Cr_2O_3含量的增加，τ_4和强度I_4急剧下降，τ_3和强度I_3基本不变。随着Cr_2O_3含量的增加，多普勒展宽系数S也急剧减小。CDB光谱的详细分析表明，parapositronium（p-Ps）的强度也随着Cr2 O3含量的增加而降低。这表明o-Ps寿命τ 4的变化是由于Cr_2O_3的化学猝灭而不是由于电子偶素的自旋转换。O-Ps强度I_4的降低表明Cr_2O_3也抑制了正电子偶素的形成。
The pore structure of Cr2O3/Al2O3catalysts and the surface chemical properties of these pores were characterized by positron lifetime and coincidence Doppler broadening (CDB) measurements. Four lifetime components could be resolved from the positron lifetime spectrum, with two long lifetime components and two short lifetime components. The two long lifetimesτ4andτ3are attributed to ortho-positronium (o-Ps) annihilation in large pores and microvoids, respectively. With increasing Cr2O3content, bothτ4and its intensityI4show sharp decrease, whileτ3and its intensityI3keep nearly unchanged. The Doppler broadeningSparameters also show sharp decrease with increasing Cr2O3content. Detailed analysis of the CDB spectrum reveals that the parapositronium (p-Ps) intensity also decreases with increasing Cr2O3content. This indicates that the change of o-Ps lifetimeτ4is due to the chemical quenching by Cr2O3but not spin-conversion of positronium. The decrease of o-Ps intensityI4indicates that Cr2O3also inhibits positronium formation.