Chemical States of Fe atoms Implanted into Solid Oxygen

我们用短寿命的~（40）<57>Mn（T_（1/2）=1.5 min）离子束进行了在束穆斯堡尔谱实验，以研究~（40）Mn注入固体氧后产生的~（<57>40）Fe原子<57>的新化学物种。预计氧的高电子亲和力有利于Fe的高价态的产生。<57>Mn粒子作为次级RI束在^<58>Fe束（E=63 MeV/核子）与Be产生靶的核射弹碎裂反应之后产生，并由RIKEN加速器研究设施的使用RIPS（Riken射弹碎片分离器）的飞行中同位素分离器分离。随后，将~<57>（13）Mn离子穿过适当厚度的Al板后注入到固体O_2样品中，将束流能量抑制到20 MeV/核子左右。在18、32和40 K下测量了1 Mn离子注入过程中的在束穆斯堡尔谱<57>。在18 K下得到的光谱可以用4组洛伦兹偶线进行分析。根据穆斯堡尔参数的同分异构位移和四极分裂以及从头算分子轨道计算，这4个组分被指定为Fe（O_2），FeO和（O_2）Fe（O_2），以及Fe原子处于较高氧化态的化学物种。本文讨论了在低温下，<57>由Mn生成的Fe原子<57>与固体O_2基体的反应产物，并与Ar基体中的O_2气体与激光烧蚀Fe原子的反应产物进行了比较。

We have performed an in-beam Mossbauer spectroscopic experiment using a short-lived ^<57>Mn(T_<1/2>=1.5 min) beam, in order to study the production of the novel chemical species of ^<57>Fe atoms arising from ^<57>Mn implanted into solid oxygen. It is expected that the high electron affinity of oxygen favors the production of high valence states of Fe.^<57>Mn particles were produced as a secondary RI beam following a nuclear projectile-fragmentation reaction of ^<58>Fe beams (E=63 MeV/nucleon) with Be production target, and separated by the in-flight isotope separator using RIPS(Riken Projectile-fragment Separator) in RIKEN Accelerator Research Facility. Subsequently, the ^<57>Mn was implanted into a solid O_2 sample after passing through an Al plate with an appropriate thickness to suppress the beam energy down to about 20 MeV/nucleon. The in-beam Mossbauer spectra were measured at 18, 32 and 40 K during the implantation of ^<57>Mn. The obtained spectrum at 18 K could be analyzed by 4 sets of Lorentzian doublet. From the basis of Mossbauer parameters of the isomer shifts and the quadrupole splittings and the ab-initio molecular orbital calculations, these 4 components were assigned to be Fe(O_2), FeO, and (O_2)Fe(O_2), and a chemical species in a higher oxidation state of Fe atoms. We discussed the reaction products between ^<57>Fe atoms arising from ^<57>Mn and a solid O_2 matrix, compared with the products of laser-ablated Fe atoms with O_2 gas isolated in the Ar matrix at low temperatures.