Gutsev G L, López Peña H A, McPherson S L, Boateng D Ampadu, Ramachandran B R, Gutsev L G, Tibbetts K M
Department of Physics, Florida A&M University, Tallahassee, Florida 32307, United States.
Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States.
J Phys Chem A. 2020 Apr 23;124(16):3120-3134. doi: 10.1021/acs.jpca.0c00686. Epub 2020 Apr 10.
We report density functional theory computations and photoionization mass spectrometry measurements of aniline and its positively charged ions. The geometrical structures and properties of the neutral and singly, doubly, and triply positively charged aniline are computed using density functional theory with the generalized gradient approximation. At each charge, there are multiple isomers closely spaced in total energy. Whereas the lowest energy states of both neutral and cation have the same topology CH-NH, the dication and trication have the CNH-CH topology with the nitrogen atom in the meta- and para-positions, respectively. We compute the dissociation pathways of all four charge states to NH or NH and NH or NH, depending on the initial charge of the aniline precursor. Dissociation leading to the formation of NH (from the neutral and cation) and NH (from the dication and trication) proceeds through multiple transition states. On the contrary, the dissociation of NH (from the neutral and cation) and NH (from the dication and trication) is found to proceed without an activation energy barrier. The trication was found to be stable toward abstraction on NH and NH by 0.96 and 0.18 eV, respectively, whereas the proton affinity of the trication is substantially higher, 1.98 eV. The mass spectra of aniline were recorded with 1300 nm, 20 fs pulses over the peak intensity range of 1 × 10 to 3 × 10 W cm. The analysis of the mass spectra suggests high stability of both dication and trication to fragmentation. The formation of the fragment NH and NH ions is found to proceed via Coulomb explosion.
我们报告了苯胺及其带正电荷离子的密度泛函理论计算和光电离质谱测量结果。使用广义梯度近似的密度泛函理论计算了中性、单正、双正和三正电荷苯胺的几何结构和性质。在每个电荷状态下，都有多个异构体，它们的总能量非常接近。中性和阳离子的最低能量状态具有相同的拓扑结构CH-NH，而双阳离子和三阳离子具有CNH-CH拓扑结构，氮原子分别位于间位和对位。我们计算了所有四种电荷状态分解为NH或NH以及NH或NH的途径，这取决于苯胺前体的初始电荷。导致形成NH（从中性和阳离子）和NH（从双阳离子和三阳离子）的分解通过多个过渡态进行。相反，发现NH（从中性和阳离子）和NH（从双阳离子和三阳离子）的分解没有活化能垒。发现三阳离子对NH和NH的抽取分别稳定0.96和0.18 eV，而三阳离子的质子亲和力则高得多，为1.98 eV。在1×10至3×10 W cm的峰值强度范围内，用1300 nm、20 fs脉冲记录了苯胺的质谱。质谱分析表明双阳离子和三阳离子对碎片化具有高稳定性。发现碎片NH和NH离子的形成是通过库仑爆炸进行的。
