Zhang Jinglai, Wu Wenpeng, Wang Lianbin, Cao Zexing
College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475001, China.
J Chem Phys. 2006 Mar 28;124(12):124319. doi: 10.1063/1.2179068.
Structures and stabilities of carbon chains C(2n)S and C2(n)Cl+ (n=1-5) in their ground states have been investigated by the density functional theory and the coupled cluster approach using single and double substitutions. The complete active space self-consistent-field method has been used for geometry optimization of selected excited states in both series. Calculations show that both C(2n)S (n=1-5) and C2(n)Cl+ (n=3-5) have linear structures in the triplet ground state 3Sigma-, while C2Cl+ and C4Cl+ have nonlinear structures in the ground state 3A". The vertical transition energies and emission energies by the multiconfigurational second-order perturbation theory in linear clusters C(2n)S and C2(n)Cl+ exhibit similar size dependences. In comparison with the available experimental observations, the predicted excitation energies for the allowed 2 3Sigma- <--X 3Sigma- transitions have an accuracy of no more than 0.24 eV. Spin-orbit coupling configuration interaction calculations indicate that the spin-forbidden 2 1Sigma+<--X 3Sigma- transition in these species has an oscillator strength with the magnitude of 10(-4)-10(-5), and they may be observable experimentally.
利用密度泛函理论和含单双取代的耦合簇方法，研究了碳链C(2n)S和C2(n)Cl⁺（n = 1 - 5）基态的结构和稳定性。采用完全活性空间自洽场方法对这两个系列中选定激发态进行几何优化。计算表明，C(2n)S（n = 1 - 5）和C2(n)Cl⁺（n = 3 - 5）在三重态基态³Σ⁻中具有线性结构，而C2Cl⁺和C4Cl⁺在基态³A″中具有非线性结构。线性簇C(2n)S和C2(n)Cl⁺中通过多组态二阶微扰理论得到的垂直跃迁能和发射能表现出相似的尺寸依赖性。与现有的实验观测结果相比，预测的允许的2³Σ⁻ ← X³Σ⁻跃迁的激发能精度不超过0.24 eV。自旋轨道耦合组态相互作用计算表明，这些物种中自旋禁阻的2¹Σ⁺ ← X³Σ⁻跃迁的振子强度大小为10⁻⁴ - 10⁻⁵，它们可能在实验中被观测到。
