Universidade de São Paulo, Instituto de Química, Departamento de Química Fundamental, Av. Prof. Lineu Prestes, 748, São Paulo, São Paulo, 05508-000, Brazil.
J Chem Phys. 2012 Oct 21;137(15):154302. doi: 10.1063/1.4758475.
We present a detailed theoretical study of the stability of the gas-phase diatomic dications SnF(2+), SnCl(2+), and SnO(2+) using ab initio computer calculations. The ground states of SnF(2+), SnCl(2+), and SnO(2+) are thermodynamically stable, respectively, with dissociation energies of 0.45, 0.30, and 0.42 eV. Whereas SnF(2+) dissociates into Sn(2+) + F, the long range behaviour of the potential energy curves of SnCl(2+) and SnO(2+) is repulsive and wide barrier heights due to avoided crossing act as a kind of effective dissociation energy. Their equilibrium internuclear distances are 4.855, 5.201, and 4.852 a(0), respectively. The double ionisation energies (T(e)) to form SnF(2+), SnCl(2+), and SnO(2+) from their respective neutral parents are 25.87, 23.71, and 25.97 eV. We combine our theoretical work with the experimental results of a search for these doubly positively charged diatomic molecules in the gas phase. SnO(2+) and SnF(2+) have been observed for prolonged oxygen ((16)O(-)) ion beam sputtering of a tin metal foil and of tin (II) fluoride (SnF(2)) powder, respectively, for ion flight times of about 10(-5) s through a magnetic-sector mass spectrometer. In addition, SnCl(2+) has been detected for (16)O(-) ion surface bombardment of stannous (tin (II)) chloride (SnCl(2)) powder. To our knowledge, SnF(2+) is a novel gas-phase molecule, whereas SnCl(2+) had been detected previously by electron-impact ionization mass spectrometry, and SnO(2+) had been observed before by spark source mass spectrometry as well as by atom probe mass spectrometry. We are not aware of any previous theoretical studies of these molecular systems.
我们使用从头计算计算机程序对气相双原子二价阳离子 SnF(2+)、SnCl(2+) 和 SnO(2+)的稳定性进行了详细的理论研究。SnF(2+)、SnCl(2+) 和 SnO(2+)的基态分别在热力学上是稳定的，其离解能分别为 0.45、0.30 和 0.42 eV。SnF(2+)离解为 Sn(2+) + F，而 SnCl(2+) 和 SnO(2+)的势能曲线的长程行为是排斥的，由于避免交叉作用而产生的宽势垒高度起到了一种有效的离解能的作用。它们的平衡核间距分别为 4.855、5.201 和 4.852 a(0)。形成 SnF(2+)、SnCl(2+) 和 SnO(2+)所需的双电离能 (T(e)) 分别为 25.87、23.71 和 25.97 eV。我们将理论工作与在气相中寻找这些双正电荷二原子分子的实验结果相结合。SnO(2+)和 SnF(2+)已经在长时间的氧((16)O(-))离子束溅射锡金属箔和锡(II)氟化物(SnF(2))粉末中观察到，对于约 10(-5) s 的离子飞行时间，通过磁扇区质谱仪。此外，SnCl(2+)已经在锡(II)氯化物(SnCl(2))粉末的(16)O(-)离子表面轰击中检测到。据我们所知，SnF(2+)是一种新型的气相分子，而 SnCl(2+)先前已经通过电子碰撞电离质谱法检测到，SnO(2+)先前已经通过火花源质谱法以及原子探针质谱法观察到。我们不知道以前对这些分子系统的任何理论研究。
