Departamento de Quimica, CEQUINOR, Centro de Quimica Inorganica (CONICET, UNLP), Facultad de Ciencias Exactas, UNLP, C. C. 962, 1900 La Plata, Argentina.
J Chem Phys. 2011 Jul 21;135(3):034306. doi: 10.1063/1.3613624.
In the present combined experimental and theoretical study we report the observation of the novel gas-phase dication CuZn(2+) and provide some theoretical insight into the electronic binding of this exotic metastable molecule and its formation mechanism. Using mass spectrometry we have detected four isotopomer signals of CuZn(2+) at half-integer m/z values for ion flight times of about 14 μs. CuZn(2+) was unambiguously identified by its isotopic abundance. High-current energetic Ar(+) ion bombardment of a brass surface was used for its production. Subsequent dication formation was found to take place in the ion extraction region of our mass spectrometer several tens of microns in front of the sputtered brass surface. The dication formation mechanism appears to be resonant electron transfer in soft gas-phase collisions between sputter-ejected singly charged CuZn(+) molecular ions and incoming Ar(+) projectiles. This conclusion is supported by our theoretical study that obtained an ionization energy of CuZn(+) of 15.75 eV, in excellent agreement with both the experimental and calculated ionization energy of Ar (15.76 and 15.67 eV, respectively). The ground state of CuZn(2+) is found to be a metastable one with a very shallow potential well at an internuclear equilibrium distance of about 2.7 Å the dissociation energy being very difficult to estimate. Interestingly, spin-orbit corrections are found to be necessary to get an adequate description of the metastable state of CuZn(2+), whereas relativistic corrections have no effects on neutral CuZn nor on CuZn(+).
在目前的实验和理论研究中，我们报告了新型气相二价铜锌（CuZn(2+)）的观测结果，并对这种奇异的亚稳态分子的电子结合及其形成机制提供了一些理论见解。我们使用质谱法在约 14 μs 的离子飞行时间处检测到 CuZn(2+)的四个同位素信号的半整数 m/z 值。通过其同位素丰度，CuZn(2+)被明确识别。使用高能 Ar(+)离子对黄铜表面进行强电流轰击来产生 CuZn(2+)。随后发现二价离子的形成发生在我们质谱仪的离子提取区域中，距离溅射黄铜表面数十微米。二价离子的形成机制似乎是在溅射喷射的单电荷 CuZn(+)分子离子与入射的 Ar(+)射弹之间的软气相碰撞中发生的共振电子转移。这一结论得到了我们的理论研究的支持，该研究获得了 CuZn(+)的电离能为 15.75 eV，与实验和计算的 Ar 电离能（分别为 15.76 和 15.67 eV）非常吻合。CuZn(2+)的基态被发现是一种亚稳态，其在核间平衡距离约为 2.7 Å 的势阱非常浅，离解能极难估计。有趣的是，发现自旋轨道修正对于获得 CuZn(2+)的亚稳态的充分描述是必要的，而相对论修正对中性 CuZn 或 CuZn(+)没有影响。
