Department of Chemistry, Siedlce University, 3 Maja 54, 08-110 Siedlce, Poland.
Rapid Commun Mass Spectrom. 2012 Sep 15;26(17):2093-8. doi: 10.1002/rcm.6324.
Low-energy secondary electrons are formed when energetic particles interact with matter. High-energy electrons or ions are used to form metallic structures from adsorbed organometallic molecules like W(CO)(6) on surfaces. We investigated low-energy electron attachment to W(CO)(6) in the gas phase to elucidate possible reactions during surface modification.
Two crossed electron/molecular beam setups were utilised: (i) a high-resolution electron monochromator combined with a quadrupole mass spectrometer which was used for the measurement of relative cross sections as a function of the electron energy, and (ii) a double focusing mass spectrometer used for measurements of metastable decays of anions.
The study was performed in the electron energy range between ~0 and 14 eV. W(CO)(6) efficiently decomposed upon attachment of a low-energy electron and no stable W(CO)(6)(-) anion was observed on mass spectrometric time scales. The transient negative ion formed lost instead sequentially CO ligands. The fragment anions W(CO)(5)(-), W(CO)(4)(-), W(CO)(3)(-), and W(CO)(2)(-) were observed. However, no W(-) was detectable.
Dissociative electron attachment (DEA) to W(CO)(6) led to strong dissociation but a complete loss of all CO ligands was not observed in DEA. Deposit contaminations might be a direct result of DEA reactions close to the irradiation spot in beam deposition techniques.
当高能粒子与物质相互作用时，会形成低能二次电子。高能电子或离子用于从吸附在表面上的有机金属分子（如 W(CO)(6)）形成金属结构。我们研究了气相中 W(CO)(6)对低能电子的附加作用，以阐明表面修饰过程中可能发生的反应。
使用了两个交叉的电子/分子束装置：（i）高分辨率电子单色仪与四极质谱仪结合，用于测量电子能量函数下的相对截面，（ii）双聚焦质谱仪用于测量阴离子的亚稳态衰变。
研究在电子能量范围为~0 到 14 eV 之间进行。W(CO)(6)在低能电子附着时有效分解，在质谱时间尺度上没有观察到稳定的 W(CO)(6)(-)阴离子。形成的瞬态负离子依次失去 CO 配体。观察到碎片阴离子 W(CO)(5)(-)、W(CO)(4)(-)、W(CO)(3)(-)和 W(CO)(2)(-)。然而，没有检测到 W(-)。
W(CO)(6)的电子附加解离（DEA）导致强烈的解离，但在 DEA 中没有观察到所有 CO 配体的完全损失。在束沉积技术中，靠近辐照点的 DEA 反应可能直接导致沉积污染。
